Chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO)

Comparative study of radio-clinical parameters in pediatric forms of fibrous dysplasia and chronic recurrent multifocal osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disease with clinical and radiological symptoms that overlap with fibrous dysplasia (FD), particularly in children. This study aimed to compare the clinical and radiological features of craniofacial CRMO and FD in a pediatric population. Seven children with CRMO and 14 with FD were retrospectively identified in our tertiary centre between 2012 and 2022. Their clinical, radiological, and biological (when available) data were collected. Two experienced radiologists reviewed imaging modalities following a standardized form, including characteristics of the lesions, soft-tissue involvement, and signal abnormalities (MRI). Swelling and pain were common symptoms in the CRMO group (7/7 and 5/5, respectively), compared with 11/14 and 2/14 patients in the FD group. Imaging (CT scan) comparisons revealed a predominance of erosive lesions, cortical interruption, periosteal apposition, and soft-tissue involvement in CRMO compared with FD (4/5 vs 0/6, p1 = 0.01; 5/5 vs 1/6, p2 = 0.01; 5/5 vs 0/6, p3 = 0.002; and 4/5 vs 0/6, p4 = 0.02, respectively). Hyperosteosis was mainly associated with FD lesions (6/6 vs 2/5, p = 0.06). Knowledge of the clinical and radiographic differences between CRMO and FD could help clinicians to differentiate between the two diseases.

[Arthritis and osteomyelitis in childhood and adolescence-Bacterial and nonbacterial]

Bacterial arthritis and osteomyelitis are usually acute diseases, which in this way differ from the often insidious course of nonbacterial osteomyelitis; however, there is often an overlap both in less acute courses of bacterial illnesses and also in nonbacterial osteitis. The overlapping clinical phenomena can be explained by similar pathophysiological processes. In bacteria-related illnesses the identification of the pathogen and empirical or targeted anti-infectious treatment are prioritized, whereas no triggering agent is known for nonbacterial diseases. The diagnostics are based on the exclusion of differential diagnoses, clinical scores and magnetic resonance imaging (MRI). An activity-adapted anti-inflammatory treatment is indicated.

Long-term effectiveness of the combination of iguratimod and alendronate in SAPHO syndrome: a prospective cohort study

OBJECTIVE

To evaluate the long-term effectiveness of the combination of Iguratimod (IGU) and Alendronate for patients with Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis (SAPHO) syndrome.

METHODS

A prospective cohort study was conducted on patients diagnosed with SAPHO syndrome at Peking University Third Hospital and Beijing Jishuitan Hospital from 2017 to 2024. The initial treatment regimen comprised a combination of IGU and Alendronate. Patients who were followed up for >2 years were included in our study. We collected demographic data, clinical symptoms, recurrence rates, treatment duration and overall response to therapy for all patients.

RESULTS

Seventeen patients were recruited for our cohort, with a median (IQR) follow-up of 2.91 (2.34) years. The mean treatment duration was 39.10 months. Among patients with osteoarticular involvement (17/17), 35.30% (6/17) achieved complete improvement without any recurrence, 11.76% (2/17) showed partial improvement and 52.94% (9/17) experienced intermittent flares. For patients with skin involvement (11/17), 63.64% (7/11) achieved complete improvement, 27.27% (3/11) had partial improvement and 9.09% (1/11) experienced intermittent recurrence. Notably, 88.26% (15/17) regained complete independence and resumed work, and 94.12% (16/17) experienced alleviation of anxiety and insomnia. By the end of last follow-up, 52.94% (9/17) had ceased treatment after a mean duration of 25.22 months and 22.22% (2/9) of them encountered recurrence.

CONCLUSION

The combination of IGU and Alendronate as initial treatment may be effective for the long-term management of SAPHO syndrome. ∼41% of the patients could discontinue treatment after more than two years without recurrence.

Inflammatory bowel disease in paediatric rheumatological diseases

INTRODUCTION

Rheumatological diseases (RD) in childhood are systemic diseases that occur on the basis of auto-immunity or inflammation, and they can be accompanied by inflammatory bowel disease (IBD). When there is no knowledge of this association, the treatments applied may not be sufficient and/or treatments given for RD may even lead to aggrevation of IBD findings. Thus, early identification of an association is crucial for the correct management of the diseases.

OBJECTIVES

The aim of this study is to show the frequency of IBD in patients with RDs. We also aimed to investigate in which cases IBD should be suspected in children with RDs.

METHODS

Electronic medical records of the patients who were followed up between 2012 and 2024 with a diagnosis of RD in our Paediatric Rheumatology Unit and diagnosed with IBD were reviewed retrospectively.

RESULTS

Between 2012 and 2024, 20 (3%) of 650 familial Mediterranean fever (FMF) patients, 3 (7.5%) of 40 chronic nonbacterial osteomyelitis (CNO) patients (one of them also had FMF) and 2 (1.2%) of 170 juvenile idiopathic arthritis (JIA) patients were diagnosed with IBD. While 15 (62.5%) of the patients received a RD as the initial diagnosis, 9 (37.5%) of them were initially diagnosed with IBD and then referred to rheumatology for their symptoms. The median age at the diagnosis of RD was 9 years (inter quartile range (IQR), 14.5). The median age at the diagnosis of IBD was 12 years (IQR, 13), and 12 patients (50%) had Crohn's disease (CD), 10 patients (41.6%) ulcerative colitis (UC) and 2 patients (8.4%) undeterminated disease. Although majority of the patients had classical findings of IBD, 4 patients presented with more vague symptoms including treatment-resistant iron deficiency anaemia, perianal abscess, weight loss and growth retardation.

CONCLUSIONS

RD and IBD share similar pathological pathways and clinical findings, and IBD can accompany to various RD. The diagnosis of IBD should be considered in the presence of rare and atypical symptoms. Furthermore, RD should also be considered in children with IBD who have complex extraintestinal symptoms. Key Points • RD, especially FMF, JIA and CNO, may be associated with IBD. • Paediatric rheumatologists should consider IBD as a potential diagnosis in the presence of atypical findings that may develop during the course of RD. • The co-existence of RD and IBD is important both in terms of disease progression and treatment decisions.

Chronic Non-Bacterial Osteomyelitis (CNO) in a Tertiary Center in Southern Italy: Response to Treatment and Outcome Stratification

Background/Objectives: Chronic non-bacterial osteomyelitis (CNO) is a rare autoinflammatory disease characterized by chronic sterile uni- or multifocal osteomyelitis. The treatment of CNO is mostly empirical and the outcome of the disease has not yet been standardized. The aims of this study were to correlate clinically active lesions with radiological signs of inflammation and to evaluate the outcomes in terms of symptoms and radiological signs with Whole Body Magnetic Resonance Imaging (WB-MRI) based on the treatment line used. Methods: A retrospective, observational cohort study of 20 CNO patients, recruited from a single tertiary center in southern Italy, was conducted. Patients included in the study were treated based on the "step-up" approach and were guided by the "treat-to-target" strategy as well as by the response to therapy. The outcome measure was stratified into four different groups, defined by a "Delphy consensus", depending on the symptoms and the presence of bone lesions in WB-MRI, compared with the therapy carried out. Results: Pain was the most common presenting symptom of the disease. Only 15% of our patients reported long-term complications. WB-MRI was performed for each patient both at diagnosis and during follow-up. At onset, the site most affected by the disease was the tibia. All patients who reached a 5-year follow-up (30%, n = 6) achieved a complete disease remission. Conclusions: The standardized "step-up" treatment approach in our cohort proved effective in disease management with disease control or remission in nearly 90% of patients at one year from diagnosis.

Challenges in the imaging and diagnosis of chronic non-bacterial osteomyelitis (CNO)

Chronic non-bacterial osteomyelitis (CNO) is a benign skeletal disorder of childhood and adolescence characterised by sterile bone inflammation that results in chronic insidious bone pain. Although it is increasingly recognised, many challenges remain in its diagnosis with patients waiting 15-24 months for diagnosis from the time of symptom onset. Prompt identification and treatment are key to reducing morbidity from CNO, which affects school attendance and can result in chronic limb or spine deformities. Identifying its imaging features, particularly its characteristic lesion distribution on whole-body MRI, remains key to diagnosis. Image-guided biopsy is also required in many cases, particularly those with clinical uncertainty around the diagnosis. We present a review of the challenges encountered in the diagnosis of CNO from a critical appraisal of the literature and our experience as a national paediatric sarcoma, rheumatology and orthopaedic centre. This review hopes to inform radiology colleagues involved in the evaluation of potential CNO patients by discussing its imaging appearances, typical MRI phenotypes, potential mimics and the role of image-guided biopsy.

Surgical Interventions in Chronic Recurrent Multifocal Osteomyelitis Affecting the Spine: A Case Report with Literature Review

Introduction

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare, skeletal, autoinflammatory disorder that predominantly affects young females. In this case-based review, we present a girl with progressive CRMO affecting the spine and causing spinal cord compression that required two surgical interventions.

Case Report

A 10-year-old girl was presented to the pediatric rheumatologist because of diffuse back pain radiating to her legs, a waddling gait, and sensitivity to palpation in the caudal cervical vertebral region for the past several months. During the extensive multidisciplinary evaluation, spine magnetic resonance imaging (MRI) revealed C7 vertebral body collapse requiring reconstructive surgery. The pathohistological findings of the vertebral body samples indicated chronic inflammation, whereas the microbiological analysis was negative. Because CRMO was suspected, indomethacin therapy was started with slow regression of initial symptoms and further regular controls by surgeon and pediatric rheumatologist. Six months after the first operation, without any symptoms, the patient underwent regular control X-ray of the cervical spine, which revealed C6 vertebral body collapse. Soon after the second reconstructive surgery, she presented with subacute thoracic pain due to Th7 vertebral collapse, as verified by repeated MRI. No other skeletal lesions were detected. Finally, the tumor necrosis factor inhibitor adalimumab was initiated, which resulted in the slow resolution of pain and the lack of new symptoms.

Conclusion

Spine involvement in CRMO can lead to serious deformities and even life-threatening fractures. Effective multidisciplinary cooperation involving experienced surgeons, radiologists, pathologists, and rheumatologists is crucial for accurate diagnosis and timely combined management of CRMO and possible complications.

Associated diseases and their effects on disease course in patients with chronic non-bacterial osteomyelitis: retrospective experience from a single center

OBJECTIVE

Chronic non-bacterial osteomyelitis (CNO) is a rare autoinflammatory bone disease associated with other chronic inflammatory diseases such as familial Mediterranean fever (FMF), juvenile idiopathic arthritis (JIA), spondylarthropathies, inflammatory bowel disease (IBD), and pyoderma gangrenosum. We aimed to describe the clinical and follow-up characteristics of patients with CNO and to compare findings between patients with and without comorbidities.

METHODS

The clinical records of patients with CNO who were followed up in our pediatric rheumatology clinic between 2018 and 2023 were reviewed. Patients were divided into two groups according to the presence or absence of comorbidities. The clinical, laboratory, and radiological characteristics and treatments of the groups were compared.

RESULTS

The study included 40 patients (65% male) diagnosed with CNO. The median (IQR) age at symptom onset was 10 (6.4) and at diagnosis was 11.5 (5.9) years. Fourteen (35%) patients had comorbidities. The comorbidities were FMF (n = 9), IBD (n = 3), uveitis (n = 3), psoriasis (n = 1) and acne conglabatae (n = 2). The group with comorbidities had higher number of bones involved (3 or more bones) (78.6% versus 42.3%) (p = 0.028), and 78.6% of patients with comorbidities received biologic treatment, while only 23.1% of patients without comorbidities were treated with biologics (p = 0.001).

CONCLUSION

Familial Mediterranean fever, uveitis, IBD, psoriasis and acne conglabata were found to be the clinical conditions associated with CNO. Patients with CNO who had comorbidities appeared to have a more severe phenotype of the disease accompanied with more bone involvement and requiring more biologic treatment. Key Points • Chronic non-bacterial osteomyelitis (CNO), an auto-inflammatory bone disease, can be seen in association with other inflammatory conditions such as familial Mediterranean fever (FMF), uveitis, inflammatory bowel disease (IBD), psoriasis, and acne conglobata. • If CNO is associated with another inflammatory disease, the number of bones involved may be higher and patients may need more intensive treatments, such as biologics. • CNO may coexist with one or more inflammatory diseases, which may exacerbate the disease phenotype.

Monocyte STAT1 phosphorylation and treatment response of JAK inhibitors in chronic nonbacterial osteomyelitis

BACKGROUND

Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory disease of unknown cause, predominantly affecting teens and young adults. The early diagnosis and management are challenging due to the lack of reliable diagnostic markers and the occasional intractable cases despite conventional anti-inflammatory treatments. Janus kinase (JAK) inhibitors have recently shown potential utility; however, reports on their use for pediatric patients with CNO remain limited, and no established biomarkers exist to monitor disease activity. We aimed to investigate the pathophysiology of CNO and explore the rapid testing methods for accurate diagnosis and also assessing the disease activity.

METHODS

We assessed intracellular phosphorylation of signal transducer and activator of transcription 1 (pSTAT1) in peripheral blood monocytes or T cells following interferon-gamma (IFNγ) stimulation, using flow cytometry in 9 patients under 15 years old with CNO. The pSTAT1 expression levels were compared with those in patients with STAT1-gain of function (STAT1-GOF) mutations (n = 5), other autoinflammatory diseases (n = 7), and healthy controls. Clinical and immunological data were monitored in 4 patients with intractable CNO treated with adjunctive JAK inhibitors, focusing on scoring scales, imaging data, lymphocyte subsets, cytokine profiles, and pSTAT1 levels.

RESULTS

Monocyte pSTAT1 expression after IFNγ stimulation was elevated at diagnosis or during active CNO, similar to levels observed in STAT1-GOF cases. The pSTAT1 levels in CNO patients were significantly higher than those in other autoinflammatory diseases (p = 0.024) or controls (p < 0.001). Notably, pSTAT1 levels in CNO monocytes fluctuated with disease activity, decreasing in 5 patients during clinical remission following conventional therapies (p = 0.016). In four intractable cases, pSTAT1 levels remained high despite conventional treatments but significantly decreased after initiating JAK inhibitors (p = 0.036). This reduction correlated with improved patient pain visual analog scale (p = 0.008), CNO clinical disease activity score (p = 0.029), and better bone and joint imaging, though cytokine levels remained unchanged.

CONCLUSIONS

The monocyte pSTAT1 levels after IFNγ stimulation reflect the activity of CNO, indicating the diagnostic utility as well as the monitoring effect of disease control. Adjunctive JAK inhibitors successfully controlled inflammation in treatment-resistant cases. Rapid pSTAT1 testing may help reduce osteo-articular complications, although the long-term adverse effects and resistance should be further investigated.

Simultaneous onset of chronic nonbacterial osteomyelitis in siblings

Chronic nonbacterial osteomyelitis (CNO) is an uncommon autoinflammatory disorder. Significant effort has recently been spent to better define and treat this disorder including development of consensus treatment protocols, validate disease activity tools, and refining classification criteria. However, the underlying immunopathogenesis of the disease remains elusive. In this report, we describe the simultaneous onset of CNO in siblings. A pathogenic gene mutation was not identified, and these sisters lacked a similar biomarker profile. This report highlights that if a genetic predisposition for CNO exists, it may be related to complex polygenic or multifactorial mechanisms of disease evolution.

Paediatric SAPHO syndrome with pleural effusion: Case report of a unique finding in a rare disease

Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is a rare autoinflammatory disease characterised by bone inflammation and skin manifestations including acne, palmoplantar pustulosis, psoriasis, or hidradenitis suppurativa. SAPHO syndrome is considered on the same spectrum as chronic nonbacterial osteomyelitis/chronic recurrent multifocal osteomyelitis, the former often being the nomenclature in adults and the latter in children. The diagnosis is made on patterns of clinical manifestations and is a diagnosis of exclusion. While skin and bone manifestations are commonly described with SAPHO syndrome, pleural involvement is rare, and few cases have been described in the literature, especially in paediatric patients. Herein we present a 14-year-old female with a past medical history of hidradenitis supprtiva, eczema, psoriasis, and a prior episode of culture-negative osteomyelitis who presented to the emergency room with chief complaints of right-sided pain with inspiration and back pain. Exam revealed palmoplantar pustulosis, hidradenitis supprativa, psoriasis, and tenderness of vertebrae. Imaging showed a right-sided pleural effusion and multiple sites of osteitis. Laboratory evaluation revealed elevated inflammatory markers, an exudative pleural effusion with neutrophilic predominance, and no evidence of malignancy, infection, or immunodeficiency. The patient was diagnosed with SAPHO syndrome and treated with naproxen, methotrexate, and golimumab with significant improvement including resolution of the pleural effusion. Paediatric SAPHO syndrome is a rare disease that classically causes osteitis and skin manifestations. This case highlights that pleural effusion can be a rare manifestation of paediatric SAPHO syndrome. Patients with suspected SAPHO syndrome with respiratory symptoms should be evaluated for pleural effusion.

Case report: Looking for relationship between type 1 diabetes and chronic recurrent osteomyelitis: short literature review and case presentation

Background

Childhood autoimmune disorders involve the immune system attacking its own tissues, leading to varied symptoms, while autoinflammatory disorders result from innate immune system dysregulation, both requiring extensive diagnosis and multidisciplinary management due to their complexity.

Case presentation

We present a unique clinical case of a teenager with a combination of autoimmune and autoinflammatory disorders. The initial manifestation of hip pain, coupled with progressive symptoms over several years and findings in multiple magnetic resonance imaging (MRI) scans, culminated in the diagnosis of chronic recurrent multifocal osteomyelitis (CRMO). Subsequently, the patient was diagnosed with type 1 diabetes (T1D), celiac disease, and juvenile idiopathic arthritis.The therapeutic course proved challenging, marked by unsuccessful attempts with nonsteroidal anti-inflammatory drugs (NSAIDs), and biphosphonates. However, a stable clinical status was ultimately achieved upon the introduction of methotrexate, concomitant with insulin therapy for diabetes and the implementation of a gluten-free diet for celiac disease.

Conclusions

Our case showed that the combination of autoimmune and autoinflammatory diseases, brought not only a challenging diagnostic process, but also complicated treatment.

Factors associated with treatment response in chronic nonbacterial osteomyelitis at a single center: a retrospective cohort study

BACKGROUND

NSAIDs are commonly used as first line therapy in chronic nonbacterial osteomyelitis (CNO) but are not effective for all patients. The objective of this study was to identify clinical variables associated with NSAID monotherapy response versus requiring second-line medication in a single-center cohort of patients with CNO.

METHODS

The charts of children with CNO who attended a CNO clinic at a quaternary care center between 1/1/05 and 7/31/21 were retrospectively reviewed. Patients were divided into 3 groups: NSAID-short (NSAID monotherapy for 3 to < 7 months), NSAID-long (NSAID monotherapy for ≥ 7 months), or second-line treatment. Patients were also categorized by which bodily regions were affected by CNO. Multiple linear and logistic regression models were constructed to predict total NSAID monotherapy days and the odds of needing second-line treatment, respectively. These models were optimized using variable combinations that minimized multicollinearity and maximized predictive power, as indicated by minimized AIC values.

RESULTS

One-hundred-sixty-four patients fulfilled inclusion criteria. Thirty-two patients were in the NSAID-short group, 62 in the NSAID-long group, and 70 in the second-line treatment group. Comparing the two NSAID groups showed that patients with unifocal disease at diagnosis required 47% fewer days of NSAIDs than those with multifocal disease. Results from logistic regression indicated that for each additional region affected, the odds of needing second line treatment increased by 1.94 times (p = 0.01) and that patients with symmetric bone lesions were 6.86 times more likely to require second-line treatment (p < 0.001).

CONCLUSIONS

Patients with unifocal CNO involvement at diagnosis were more likely to require shorter NSAID treatment. Patients with more regions affected and those with symmetric bone lesions were more likely to require second-line treatment.

Spontaneously regressing mass-like soft tissue involvement in a child with chronic non-bacterial osteomyelitis: case-based review

Chronic non-bacterial osteomyelitis (CNO) is an inflammatory bone disease, usually diagnosed in childhood. It is characterized by the presence of multifocal or unifocal osteolytic lesions that can cause bone pain and soft tissue swelling. CNO is known to have soft tissue involvement. However, soft tissue involvement large enough to give the appearance of a mass is rare. This article discusses a case of CNO with a mass-like appearance that involved soft tissue and spontaneously regressed, as well as presents CNO cases with soft tissue involvement and conducts a literature review on this subject. Our investigation revealed that edema and synovitis were the most frequently observed soft tissue involvements in association with CNO. Moreover, we also encountered myositis, a mass-like appearance, neuritis, and polyserositis within the surrounding muscles. Although, it is well known that bone inflammation tends to regress spontaneously in CNO patients which reflects the autoinflammatory nature of the disease, there is no such patient whose soft tissue involvement which has mass like appearance improved spontaneously. Therefore, we aimed to emphasize the clinical progress which can be easily underdiagnosed of CNO patients by the clinicians by presenting unique features of our patient and our detailed literature review.

Geriatric chronic recurrent multifocal osteomyelitis (CRMO) mimicking multifocal multiple myeloma: a first in an octogenarian

Chronic recurrent multifocal osteomyelitis (CRMO), an autoinflammatory bone disorder characterized by non-bacterial osteomyelitis causing recurrent multifocal bone lesions, is a well-known, yet uncommon pediatric condition that rarely affects adults; to date, it has never been diagnosed over the age of 75. The following report will discuss the first octogenarian diagnosed with CRMO and therefore represents an exceptionally rare presentation of a rare disease. An 83-year-old woman presented with progressive right shoulder, forearm, and hip pain, with associated weight loss and global weakness, requiring a wheelchair for mobility. Imaging revealed a pathologic right ulna fracture in addition to lytic lesions of the right proximal humerus and proximal femur. The clinical picture was thus that of a patient with probable multiple myeloma versus metastatic disease. After an extensive workup, however, the lesions were not malignant; histologic findings were instead suggestive of chronic osteomyelitis with negative cultures. Given the multifocal nature of this condition, combined with a lack of clinical symptoms of infection, a diagnosis of CRMO was rendered. The patient underwent intramedullary nailing of the right femur and splinting of the ulna, with a subsequent remarkable recovery to painless ambulation, complete union of the right ulna fracture, and resolution of the lytic lesions without receiving any targeted medical treatment. This case highlights the importance of maintaining CRMO on the differential for multifocal skeletal lesions, regardless of age. Performing a thorough workup with necessary imaging, biopsy, and culture are critical to establishing this diagnosis, which can only made as a diagnosis of exclusion.

Chronic non-bacterial osteomyelitis of the mandible - orthodontic considerations and management: A case report

This case report describes the orthodontic management of a case of chronic non-bacterial osteomyelitis (CNO) of the mandible, a rare non-infective variant of osteomyelitis that exhibits a marked predilection in children and adolescents. The patient presented with a unilateral facial swelling associated with fluctuating pain. Radiographic examination, along with tissue biopsy and culture, as well as multispecialty input, led to confirmation of the diagnosis. There was no clear aetiological factor and pharmacological, symptomatic management was indicated. CNO requires multidisciplinary input, with good interspecialty communication and discussion, for an accurate diagnosis. Orthodontic management should be considered on a case-by-case basis, with tailored aims appropriate for each patient.

Update on the diagnosis and treatment of CNO in children: a clinician's perspective

Chronic non-bacterial osteomyelitis (CNO) is caused by aseptic inflammation of bones, primarily driven by the innate immune system. CNO may display different clinical presentations (acute vs chronic, uni- vs multifocal) and is accompanied by other inflammatory disorders in up to a third of patients. Once considered a rare disorder, it has become clear that many patients were underdiagnosed. With increasing awareness and the development of total-body MRI protocols, CNO recognition and diagnosis have greatly improved. Our knowledge of the clinical manifestations and outcomes of CNO has been refined in recent years, especially thanks to the recruitment of large international series. Similarly, new insights into the pathogenesis have been gained by the development of mice models and identification of rare monogenic diseases that resemble CNO. Unfortunately, these advances have not been paralleled in the therapeutic management. In the absence of prospective controlled trials, therapeutic strategies still rely on low-level evidence studies. About half of the patients respond to first-line therapies, but a more refractory and/or chronic disease course requires additional treatments. This narrative review aims to provide the practicing physician with an update on CNO pathogenesis, clinical presentation, associated inflammatory conditions, and diagnostic investigations, and includes a concise summary of current therapeutic recommendations.

CONCLUSION

While major progresses have been made in the recognition and management of CNO, significant challenges remain, in particular regarding the treatment of refractory patients, and those with associated inflammatory disorders.

WHAT IS KNOWN

• Many physicians caring for children will encounter patients suffering of (suspected) CNO. CNO diagnosis requires exclusion of numerous conditions included in the differential diagnosis, which may be challenging.

WHAT IS NEW

• We provide an updated review of recent findings in the field CNO, including imaging and diagnostic strategies, associated inflammatory diseases and long-term outcomes data. • We focus particularly on the challenges encountered by clinicians in the diagnosis and treatment of these patients. • We highlight knowledge gaps in the understanding and treatment of CNO, that should stimulate future research.

Chronic nonbacterial osteomyelitis in neuroradiology - behavior and evolution of vertebral and mandibular lesions on imaging

BACKGROUND

Chronic nonbacterial osteomyelitis (CNO) is a rare non-infectious inflammatory musculoskeletal disease where imaging plays a key diagnostic role. Vertebral and mandibular lesions are frequent manifestations, meaning their awareness is crucial for the neuroradiologist to avoid delays in diagnosis and treatment.

OBJECTIVE

Characterize vertebral and mandibular CNO lesions on imaging to assist practicing neuroradiologists in better identifying this disease.

MATERIALS AND METHODS

Retrospective review of all CNO patients of our pediatric center, including only patients with vertebral or mandibular lesions. All imaging exams were analyzed to record lesion characteristics.

RESULTS

We included 13 patients (six male). The mean age of onset was 12.3 years. Ten patients had only vertebral lesions, two had only mandibular lesions, and one had both. For patients with vertebral lesions, the median number of levels affected was three, 81.8% had multiple levels affected, 90.0% had dorsal spine lesions, 72.7% had platyspondyly, and 81.8% had inflammatory changes. All vertebral lesions had at least partial resolution of inflammatory findings, the mean time of lesion activity was 2.5 years, and recurrence occurred in 27.3%. Three patients had sacral lesions, all with sacroiliitis. In patients with mandibular lesions, all had unilateral lesions involving the mandibular ramus, all had hyperostosis, periosteal reaction, bone edema, and soft tissue inflammation, all had partial resolution on follow-up, and one had recurrence.

CONCLUSION

CNO vertebral lesions are not rare, are often multiple, predominantly affect dorsal levels, and most result in vertebral height loss. Resolution of vertebral inflammatory lesions is frequent, but so is recurrence. Sacral lesions may be present and result in sacroiliitis. The mandible may be a site of unifocal disease, typically affecting the ramus, with prominent bony changes and soft tissue inflammation.

An improved understanding of pediatric chronic nonbacterial osteomyelitis pathophysiology informs current and future treatment

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease that primarily affects children and young people. It can cause significant pain, reduced function, bone swelling, and even (vertebral body) fractures. Because of a limited understanding of its pathophysiology, the treatment of CNO remains empiric and is based on relatively small case series, expert opinion, and personal experience. Several studies have linked pathological NOD-kike receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome activation and the resulting imbalance between pro- and anti-inflammatory cytokine expression with CNO. This agrees with elevated pro-inflammatory (mostly) monocyte-derived protein signatures in the blood of CNO patients that may be used as future diagnostic and/or prognostic biomarkers. Recently, rare variants in the P2RX7 gene, encoding for an ATP-dependent transmembrane channel, were linked with increased NLRP3 inflammasome assembly and prolonged monocyte/macrophage survival in CNO. Although the exact molecular mechanisms remain unclear, this will inform future target-directed and individualized treatment. This manuscript reviews most recent developments and their impact on diagnostic and therapeutic strategies in CNO.

Current and future advances in practice: SAPHO syndrome and chronic non-bacterial osteitis (CNO)

Synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome is a rare, underdiagnosed disease with a wide clinical spectrum. Sterile bone inflammation, predominantly of the anterior chest, and skin manifestations (palmoplantar pustulosis, psoriasis vulgaris and acne) are the key features of SAPHO, which shares certain similarities with SpA. SAPHO is closely related to paediatric chronic non-bacterial osteitis (CNO), a spectrum of autoinflammatory bone diseases. The aetiology of SAPHO is considered multifactorial based on a complex interplay of genetic, immune and infectious factors. Despite the increasing awareness of SAPHO/CNO, diagnostic delay is common, as validated classification and diagnostic criteria are lacking. Treatment of SAPHO represents a challenge and includes anti-inflammatory drugs, antibiotics, bisphosphonates, synthetic conventional DMARDs and off-label use of anti-cytokine biologics and Janus kinase inhibitors. This review summarizes the current diagnostic and practical treatment approach to SAPHO/CNO and highlights the ongoing research endeavours concerning the definition and validation of diagnostic criteria, core domains and treatment.

Chronic Recurrent Multifocal Osteomyelitis Involving the Spine, Sternum, and Lower Extremities: A Case Report

Chronic recurrent multifocal osteomyelitis (CRMO) or chronic nonbacterial osteitis is a sterile autoinflammatory disease of bone in children that can mimic infectious osteomyelitis and osteosarcoma. Early diagnosis, treatment, and long-term follow-up of CRMO are essential. We describe a 10-year-old boy who presented with 15 days of left ankle bone more than joint pain, swelling, and limp. Plain radiographs and magnetic resonance imaging scans were nondiagnostic of osteomyelitis and tibial irrigation and biopsy were negative for infection and malignancy. Four years later, he again presented with similar pain in his right ankle. Repeat bone biopsy noted reactive bone changes and bone culture was sterile. Whole-body magnetic resonance imaging revealed multiple enhancing lesions in the long bones of bilateral lower extremities, spine, and sternum. He was diagnosed with CRMO, and treatment with celecoxib and subsequently pamidronate, infliximab, and methotrexate were initiated. After 6 months of treatment, the patient's gait and pain improved, and 2 years later, his CRMO was in clinical and radiologic remission. Of note, he developed palmoplantar pustular psoriasis, commonly seen in CRMO, that was not determined to be from tumor necrosis factor inhibition.

A Case of Chronic Recurrent Multifocal Osteomyelitis (CRMO)

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare but underdiagnosed, severe inflammatory bone disease that primarily affects children. It's typically characterized by bone pain, especially within the metaphysis of long bones, clavicles, and vertebrae, but it can present in any bone and with varied presentation, including extraosseous symptoms that may be associated with other autoimmune/inflammatory diseases. Chronic recurrent multifocal osteomyelitis is a sterile bone disease that does not typically have an infectious source. Its pathogenesis involves the dysregulation of the innate immune system via upregulation of cytokines, inflammasomes, and osteoclastic properties. Diagnostic testing is nonspecific and includes X-ray and MRI, bone biopsy, inflammatory markers, and autoimmune markers. Chronic recurrent multifocal osteomyelitis is established by the diagnosis of exclusion. First-line treatment is nonsteroidal anti-inflammatory drugs (NSAIDs); if vertebral involvement is present, a bisphosphonate is typically added. This case report emphasizes the importance of considering CRMO as a differential diagnosis of multifocal bone pain in children.

Imaging of lower extremity infections: predisposing conditions, atypical infections, mimics, and differentiating features

Imaging evaluation for lower extremity infections can be complicated, especially in the setting of underlying conditions and with atypical infections. Predisposing conditions are discussed, including diabetes mellitus, peripheral arterial disease, neuropathic arthropathy, and intravenous drug abuse, as well as differentiating features of infectious versus non-infectious disease. Atypical infections such as viral, mycobacterial, fungal, and parasitic infections and their imaging features are also reviewed. Potential mimics of lower extremity infection including chronic nonbacterial osteomyelitis, foreign body granuloma, gout, inflammatory arthropathies, lymphedema, and Morel-Lavallée lesions, and their differentiating features are also explored.

Coexisting Sacroiliac Arthritis and Chronic Nonbacterial Osteomyelitis in an Adolescent with Ehlers-Danlos Syndrome: A Case Report and Treatment Success

BACKGROUND Chronic nonbacterial osteomyelitis (CNO) is a multifocal autoinflammatory bone disease mainly affecting children and adolescents. Sacroiliitis is an inflammation of the sacroiliac joint, diagnosed with the use of musculoskeletal MRI due to its ability to visualize active inflammatory lesions. Ehlers-Danlos syndrome (EDS) is non-inflammatory hereditary disorder of connective tissue. Here, we report the case of a 17.5-year-old female patient with classical EDS and long-term course of the CNO with coexistence of sacroiliac arthritis. CASE REPORT On admission, a patient with CNO reported pain in the scapula, thoracic spine, shoulders, and iliac region, with morning stiffness present for 5 months. Physical examination revealed knee and elbow joint hyperextension, hypermobility of the phalanges, increased range of motion of the hip joints, and the presence of reticular rash on the face. In the laboratory blood tests, minor leukocytosis was reported. During hospitalization, a whole-body MRI was performed, detecting bone marrow edema in the Th3, Th4, and Th7 vertebral bodies and the head of seventh rib on the left side, as well as bilaterally in the sacroiliac joints. The patient was diagnosed with sacroiliitis and EDS and successfully treated with risedronate sodium, methotrexate with folic acid, sulfasalazine, and meloxicam, achieving CNO remission and reduced severity of axial skeleton pain. CONCLUSIONS The coexistence of these 3 diseases - CNO, sacroiliac arthritis, and EDS - in the same patient is rare and requires interphysician collaboration to determine the correct diagnosis and subsequently arrange multi-speciality therapeutic management to achieve remission.

Bone marrow edema in children: chronic nonbacterial osteomyelitis and its mimickers

Bone marrow is a highly cellular tissue undergoing significant developmental and physiologic changes with age. Indeed, with maturation from pediatric to the adult age there is a progressive, centrifugal conversion from red to yellow bone marrow. Histological characteristics of bone marrow are reflected in MR image signal. MR is therefore extremely sensitive in detecting pathological changes which are mostly characterized by increased free water causing high signal intensity on T2. Among the numerous diseases causing bone marrow edema in children chronic nonbacterial osteomyelitis (CNO) certainly has to be mentioned. This idiopathic inflammatory disorder is characterized by nonspecific migrating symptoms like skeletal pain with phases of exacerbations and relapses with alternating acute and chronic MR signs and it is often a diagnosis of exclusion. Hence, with bone marrow edema, various features at imaging should be considered to differentiate malignancies such as osseous lymphoma, osteosarcoma, and Ewing's sarcoma as well as benign lesions like osteomyelitis, post-traumatic, or post-treatment bone marrow edema. The aim of this review is to recall the main characteristics of CNO and provide an overview of its main mimickers highlighting similarities and differences.

Scurvy in a Child Presenting With a Limp and Elevated Inflammatory Markers: A Case Report

Scurvy is a rare diagnosis in resource-rich countries, but cases have been documented in the United States in special populations of pediatric patients at increased risk of micronutrient deficiency such as those with autism spectrum disorder, developmental delay, or eating disorders. We discuss a seven-year-old female with autism spectrum disorder who presented with a limp and refusal to ambulate and elevated inflammatory markers on initial laboratory evaluation. Given her highly selective diet and malnutrition, we made a provisional diagnosis of scurvy and started treatment-dose vitamin C, which led to a significant improvement in her ambulatory function. Plasma vitamin C was ultimately undetectable. She was discharged with vitamin C supplementation and referred to a feeding clinic to address her malnutrition and selective eating.

Diagnostic Role of FDG PET/CT in Pediatric Patients With Chronic Recurrent Multifocal Osteomyelitis

PURPOSE

Chronic recurrent multifocal osteomyelitis (CRMO), or chronic nonbacterial osteomyelitis, is difficult to diagnose. The accurate diagnosis of CRMO relies on comprehensive imaging examinations because of its multifocal nature. In this regard, 18 F-FDG PET/CT has demonstrated significant utility in inflammatory diseases. This study tries to determine the value of FDG PET/CT in the evaluation of CRMO.

PATIENTS AND METHODS

We retrospectively collected imaging data from pediatric CRMO patients who underwent FDG PET/CT scans. Lesions exhibiting abnormal metabolism with/without structural abnormalities on FDG PET/CT were identified as CRMO lesions, and their location and SUV max were recorded.

RESULTS

A total of 21 pediatric patients with CRMO were included in this study. The median age at diagnosis was 9.4 years. Total 131 foci of abnormal activity were identified using FDG PET/CT imaging. The distribution pattern showed a higher prevalence of lower limbs and pelvis involvement. Among all identified lesions, abnormalities were detected on both PET and CT images of 93 lesions, whereas exclusively positive findings on 18 F-FDG PET alone were observed for 38 of them.

CONCLUSIONS

Our study findings suggest a higher prevalence of lesions in the bones of the lower limbs and pelvis among children with CRMO. Compared with CT scans, FDG PET exhibits superior sensitivity in detecting these lesions.

Two cases of smallpox from 1540 CE circum-contact (early colonial) Northern Coastal Peru

OBJECTIVE

This project seeks to create a differential diagnosis for lesions found on the skeletal remains of two children as a means to explore the presence of viral disease in 16th- century Peru.

MATERIALS

Extremely well-preserved human remains of two children who died between the ages of 1-2 years old, recovered from the circum-contact (∼1540 CE) cemetery in Huanchaco, Peru.

METHODS

Macroscopic and radiographic analysis.

RESULTS

Both individuals present with cortical thickening, symmetrical destructive lesions, metaphyseal expansion, perforations, exposure of the medullary cavity, resorption of metaphyseal ends and necrosis of the long bones, and deposited reactive new bone. These features are consistent with osteomyelitis variolosa and bacterial osteomyelitis.

CONCLUSIONS

Three features of Individuals IG-124 and IG-493 suggest a highly consistent diagnosis of osteomyelitis variolosa: multiple skeletal lesions, the historical context of the area, and the high mortality rate of non-adults in the circum-contact cemetery.

SIGNIFICANCE

Although viral infections are ubiquitous and well documented historically, their etiologies are often difficult to determine in archaeological populations. Orthopoxvirus variola (smallpox) is one of the many viruses whose archaeological impact is still under explored in skeletal remains.

LIMITATIONS

The absence of smallpox in other children from the Huanchaco cemetery creates difficulty in ascertaining true prevalence rates or information on potential outbreaks.

SUGGESTIONS FOR FURTHER RESEARCH

Further research analyzing aDNA from calculus and/or residues using a DIP-GC-MS method might create a better understanding of how smallpox spread through the region.

Collaborative approach to paediatric chronic non-bacterial osteomyelitis of the mandible: Great Ormond Street Hospital case series

This paper outlines a 10-patient case series of chronic non-bacterial osteomyelitis (CNO) of the mandible at a tertiary paediatric hospital in the UK. Our findings highlight the homogeneous presenting signs and symptoms of an intermittently painful, swollen angle and ramus of the mandible. We present the typical laboratory investigative findings (normal inflammatory markers) and imaging appearances (sclerosis and periosteal oedema). Our paper outlines an investigation protocol, including recommendations for extraoral bone biopsies and systemic magnetic resonance imaging (MRI). We explain the importance of multidisciplinary care, with combined care by rheumatologists and infectious disease specialists. Finally we demonstrate the efficacy of our treatment algorithm for oral non-steroidal anti-inflammatory drugs (NSAIDs), and in those cases refractory to NSAIDS, intravenous pamidronate. This paper provides a useful addition to the literature by informing OMF surgeons of this rare condition and given the clinical equipoise in treatments, it can hopefully guide clinicians in an investigation pathway and management protocol.

P2RX7 gene variants associate with altered inflammasome assembly and reduced pyroptosis in chronic nonbacterial osteomyelitis (CNO)

Chronic nonbacterial osteomyelitis (CNO), an autoinflammatory bone disease primarily affecting children, can cause pain, hyperostosis and fractures, affecting quality-of-life and psychomotor development. This study investigated CNO-associated variants in P2RX7, encoding for the ATP-dependent trans-membrane K+ channel P2X7, and their effects on NLRP3 inflammasome assembly. Whole exome sequencing in two related transgenerational CNO patients, and target sequencing of P2RX7 in a large CNO cohort (N = 190) were conducted. Results were compared with publicly available datasets and regional controls (N = 1873). Findings were integrated with demographic and clinical data. Patient-derived monocytes and genetically modified THP-1 cells were used to investigate potassium flux, inflammasome assembly, pyroptosis, and cytokine release. Rare presumably damaging P2RX7 variants were identified in two related CNO patients. Targeted P2RX7 sequencing identified 62 CNO patients with rare variants (32.4%), 11 of which (5.8%) carried presumably damaging variants (MAF <1%, SIFT "deleterious", Polyphen "probably damaging", CADD >20). This compared to 83 of 1873 controls (4.4%), 36 with rare and presumably damaging variants (1.9%). Across the CNO cohort, rare variants unique to one (Median: 42 versus 3.7) or more (≤11 patients) participants were over-represented when compared to 190 randomly selected controls. Patients with rare damaging variants more frequently experienced gastrointestinal symptoms and lymphadenopathy while having less spinal, joint and skin involvement (psoriasis). Monocyte-derived macrophages from patients, and genetically modified THP-1-derived macrophages reconstituted with CNO-associated P2RX7 variants exhibited altered potassium flux, inflammasome assembly, IL-1β and IL-18 release, and pyroptosis. Damaging P2RX7 variants occur in a small subset of CNO patients, and rare P2RX7 variants may represent a CNO risk factor. Observations argue for inflammasome inhibition and/or cytokine blockade and may allow future patient stratification and individualized care.

Musculoskeletal symptoms and their impact on health-related quality of life in chronic nonbacterial osteomyelitis patients

INTRODUCTION

Chronic non-bacterial osteomyelitis (CNO) is a rare, non-infection- related inflammatory disorder that affects children and teens. Clinical manifestations of CNO range widely from moderate, time-limited, monofocal inflammation of the bone to extreme multifocal or chronically active inflammation of the bone.

OBJECTIVES

The main aim of this study was to explore the correlation between musculoskeletal (MSK) symptoms and health-related quality of life (HRQoL) in patients with CNO.

METHODS

Children and adults with CNO and their parents were asked to answer a web-based survey. The survey consisted of multiple questions centered around demographic, clinical and therapeutic data, MSK discomfort form based on the Nordic MSK Questionnaire and HRQoL based on Pediatric Quality of Life Inventory-4 (PedsQL-4) and PedsQL rheumatology module. The inclusion criteria included diagnosis of CNO before the age of 18. Patients who had malignancies or any chronic rheumatic, MSK, neurological disease prior to CNO onset were excluded.

RESULTS

There was a total of 68 participants, mostly females (66.2%), with median age 14 years and median disease duration 4.75 years. The median number of bones affected by CNO was 5 and ranged from 1 to 24 bones. Among the studied patients, 45 patients (66.2%) had MSK manifestations at the last month. The most commonly affected part was ankle and feet (26.5%). Regarding HRQoL, patients with MSK manifestations had lower scores than did patients without in PedsQL-4 (p < 0.001) including domains of physical functioning (p < 0.001), emotional functioning (p = 0.033), social functioning (p < 0.001) and school functioning (p = 0.007) in addition to lower scores in PedsQL rheumatology module (p < 0.001) including domains of pain and hurt (p < 0.001), daily activities (p < 0.001), treatment (p = 0.035), worry (p = 0.001) and communication (p < 0.001).

CONCLUSION

MSK manifestations have a negative impact on HRQoL in CNO patients. So, early identification and treatment are highly recommended.

Reconstructive surgery with an autologous bone graft in a dog with presumptive chronic non-bacterial osteomyelitis

A 15-year-old Cocker Spaniel was referred to for the evaluation of left forelimb lameness. Radiographic and computed tomography examinations revealed osteolysis of the proximal left third, fourth and fifth metacarpal bones and pathological fractures of the proximal left fourth metacarpal bone. Histopathological examination via bone biopsy did not provide a definitive diagnosis, and the owner elected limb-sparing surgery. The fourth metacarpal bone and digits were amputated. Subsequently, autologous bone grafts were performed on the lytic area of the third and fifth metacarpal bones. The dog showed improvement in gait 7 weeks after reconstructive surgery. Chronic non-bacterial osteomyelitis (CNO) was diagnosed by exclusion. To the best of our knowledge, CNO has not been previously reported in dogs.

A clinico-radiological review of chronic non-bacterial osteomyelitis in paediatrics, adolescents, and adults: demystifying a forgotten differential

Chronic non-bacterial osteomyelitis (CNO), also known as non-bacterial osteitis, is a chronic autoinflammatory disease of unknown aetiology that primarily occurs in the paediatric population, although rare cases of adult-onset disease also exist. CNO has non-specific clinical and radiological presentations, and the affected population often present with bone pain of insidious onset secondary to sterile bony inflammation that can be associated with swelling, focal tenderness, and warmth at the affected sites. The pattern of bony involvement appears to be dependent on the age of onset, with adults frequently having axial skeletal lesions and children and adolescents often being affected in the appendicular skeletal sites. CNO is a diagnosis of exclusion, and imaging is heavily relied on to identify and characterise the bony lesions in addition to exclude diseases that can mimic CNO. Magnetic resonance imaging is often the reference standard with biochemical and histopathological findings being complementary. Although combining imaging methods can be used to facilitate the diagnosis, a single technique could be adequate depending on the clinical picture. Given the relatively rare incidence of CNO, limited awareness of the disease among care providers, and its similarity in clinical and radiological presentation to various bony diseases, there are often long delays in diagnosis, with adults being unfavourably affected compared to paediatrics and adolescents. This review of CNO will describe the condition, overview its clinical presentation, highlight the radiological features, and emphasise clinical pearls that can aid in diagnosis and ruling out the mimics.

Unique Bilaterally Symmetrical Multifocal Osteomyelitis Presentation in a Health-care Worker with Sickle Cell Disease Secondary to Klebsiella Infection - A Case Report

Introduction

Osteomyelitis is one of the most common infectious complications in people with sickle cell disease (SCD). The most common infecting organisms in SCD are the Salmonella species and Staphylococcus aureus; Streptococcus pneumoniae and Bacteroides species have also been described, however, osteomyelitis attributable to infection with hypervirulent Klebsiella spp. is a rare entity. We describe our experience with a rare presentation of multifocal bilateral symmetrical ulna and fibula osteomyelitis in a patient with SCD due to Klebsiella bacteremia with 1-year follow-up.

Case Report

A 25-year-old female known SCD since childhood who underwent treatment for dengue at our hospital had her blood cultures positive for Klebsiella, following which she was treated with appropriate antibiotics. Two weeks following the asymptomatic period patient presented with complaints of pain over the bilateral forearm and legs. The patient was evaluated for laboratory parameters and plain radiograph of the bilateral forearm and bilateral legs. The radiological features were suggestive of osteomyelitis, showing "Bilaterally symmetrical involvement." Laboratory parameters erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were found raised. The patient was planned for biopsy and debridement of the lesion from the right ulna. The culture from the biopsy showed growth of Klebsiella sp. and was sensitive to co-trimoxazole. The patient was started on co-trimoxazole for 6 weeks and had a significant clinical improvement in the form of subsidence of pain, normalization of the blood counts along with the acute phase reactants (ESR, CRP).

Conclusion

Our case contributes to the growing awareness of the unusual manifestations of this serious disease and the rarity of bilateral symmetrical involvement. Our case highlights the importance of clinician awareness, manifestations, and management of Klebsiella sp. hypervirulent strains.

Clinical and imaging features of six Han patients with SAPHO syndrome

BACKGROUND

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare autoimmune disease characterized by skin or osteoarticular damage. SAPHO syndrome is often misdiagnosed or missed diagnosis due to lack of overall understanding of the disease by clinicians.

PURPOSE

To analyze the clinical symptoms and imaging features of six Han patients with SAPHO syndrome in order to provide reference for doctors to diagnose SAPHO syndrome.

MATERIAL AND METHODS

This study retrospectively analyzed the clinical data of six Han patients with SAPHO syndrome.

RESULTS

All six Han patients with SAPHO syndrome had severe acne or pustulosis of the hands and feet, and all of them had osteoarticular damage, including five cases involving the sternoclavicular joint. Some patients showed a specific and typical "bull's head" sign on 99mTc-labeled methylene diphosphonate bone imaging. Among the six patients recruited, there was one thoracic vertebra, one cervical vertebra, one sacroiliac joint, and one peripheral joint involvement. Two patients had limited activity due to severe osteoarticular damage.

CONCLUSION

Due to the atypical clinical symptoms of SAPHO syndrome, most patients will experience a tortuous and long diagnostic process, while a correct understanding and timely intervention of SAPHO syndrome are essential to improve the prognosis of patients.

Garrè Sclerosing Osteomyelitis of the Clavicle: Clinical Results after Clavicular Resection

(1) Background: Chronic non-bacterial osteomyelitis (CNO), also known as sclerosing osteomyelitis of Garrè, is a rare inflammatory bone disease with a specific clinical picture, uncertain pathogenesis, and no consensus on an effective treatment. Most frequently affecting other long bones, CNO may rarely involve the clavicle. The aim of this study was to present the results of a series of patients affected by CNO of the clavicle treated with total and partial clavicula resection. In addition, a literature review of different types of treatment of CNO was performed. (2) Methods: We retrospectively reviewed three patients with Sclerosing Osteomyelitis of Garre' of the clavicle treated with partial resection of the clavicle (one) and with total clavicular resection (two). (3) Results: Patients (two female and one male) were an average age of 35.7 years at the time of the operation. At the 4-year follow-up, the mean active ROM was: 143° forward flexion, 133° abduction, 42° external rotation with an internal rotation of two patients at the interscapular level and one patient at the lumbosacral junction. The mean ASES score was 92/100 (range 87-100). In the literature review, after screening the abstracts and full texts for eligibility, 34 studies met the inclusion criteria. Conclusions: Partial or total clavicular resection resulted an effective treatment of CNO of the clavicle. The procedure seems to be particularly indicated after the failure of more conservative treatments.

Machine Learning Algorithm: Texture Analysis in CNO and Application in Distinguishing CNO and Bone Marrow Growth-Related Changes on Whole-Body MRI

OBJECTIVE

The purpose of this study is to analyze the texture characteristics of chronic non-bacterial osteomyelitis (CNO) bone lesions, identified as areas of altered signal intensity on short tau inversion recovery (STIR) sequences, and to distinguish them from bone marrow growth-related changes through Machine Learning (ML) and Deep Learning (DL) analysis.

MATERIALS AND METHODS

We included a group of 66 patients with confirmed diagnosis of CNO and a group of 28 patients with suspected extra-skeletal systemic disease. All examinations were performed on a 1.5 T MRI scanner. Using the opensource 3D Slicer software version 4.10.2, the ROIs on CNO lesions and on the red bone marrow were sampled. Texture analysis (TA) was carried out using Pyradiomics. We applied an optimization search grid algorithm on nine classic ML classifiers and a Deep Learning (DL) Neural Network (NN). The model's performance was evaluated using Accuracy (ACC), AUC-ROC curves, F1-score, Positive Predictive Value (PPV), Mean Absolute Error (MAE) and Root-Mean-Square Error (RMSE). Furthermore, we used Shapley additive explanations to gain insight into the behavior of the prediction model.

RESULTS

Most predictive characteristics were selected by Boruta algorithm for each combination of ROI sequences for the characterization and classification of the two types of signal hyperintensity. The overall best classification result was obtained by the NN with ACC = 0.91, AUC = 0.93 with 95% CI 0.91-0.94, F1-score = 0.94 and PPV = 93.8%. Between classic ML methods, ensemble learners showed high model performance; specifically, the best-performing classifier was the Stack (ST) with ACC = 0.85, AUC = 0.81 with 95% CI 0.8-0.84, F1-score = 0.9, PPV = 90%.

CONCLUSIONS

Our results show the potential of ML methods in discerning edema-like lesions, in particular by distinguishing CNO lesions from hematopoietic bone marrow changes in a pediatric population. The Neural Network showed the overall best results, while a Stacking classifier, based on Gradient Boosting and Random Forest as principal estimators and Logistic Regressor as final estimator, achieved the best results between the other ML methods.

Treatment and monitoring of SAPHO syndrome: a systematic review

BACKGROUND AND OBJECTIVES

Synovitis acne pustulosis hyperostosis osteitis (SAPHO) is a rare heterogeneous disease of unknown aetiopathology. Externally validated and internationally agreed diagnostic criteria or outcomes and, as a result, prospective randomised controlled trials in SAPHO are absent. Consequently, there is no agreed treatment standard. This study aimed to systematically collate and discuss treatment options in SAPHO.

METHODS

Following 'Preferred Reporting Items for Systematic Reviews and Meta-Analyses' guidance, a systematic literature search was conducted using PubMed, Scopus and Web of Science databases. Prospective clinical studies and retrospective case collections discussing management and outcomes in SAPHO involving five or more participants were included. Articles not published in English, studies not reporting defined outcomes, and studies solely relying on patient-reported outcomes were excluded.

RESULTS

A total of 28 studies (20 observational, 8 open-label clinical studies) reporting 796 patients of predominantly European ethnicity were included. Reported therapies varied greatly, with many centres using multiple treatments in parallel. Most patients (37.1%) received non-steroidal anti-inflammatory drugs alone or in combination. Bisphosphonates (22.1%), conventional (21.7%) and biological (11.3%) disease-modifying antirheumatic drugs were the next most frequently reported treatments. Reported outcomes varied and delivered mixed results, which complicates comparisons. Bisphosphonates demonstrated the most consistent improvement of osteoarticular symptoms and were associated with transient influenza-like symptoms. Paradoxical skin reactions were reported in patients treated with TNF inhibitors, but no serious adverse events were recorded. Most treatments had limited or mixed effects on cutaneous involvement. A recent study investigating the Janus kinase inhibitor tofacitinib delivered promising results in relation to skin and nail involvement.

CONCLUSIONS

No single currently available treatment option sufficiently addresses all SAPHO-associated symptoms. Variable, sometimes descriptive outcomes and the use of treatment combinations complicate conclusions and treatment recommendations. Randomised clinical trials are necessary to generate reliable evidence.

Chronic Nonbacterial Osteomyelitis in Inflammatory Bowel Disease

Chronic nonbacterial osteomyelitis (CNO), also known as chronic recurrent multifocal osteomyelitis (CRMO), is a rare autoinflammatory bone disease primarily affecting children and adolescents. This review presents a comprehensive analysis of the intricate relationship between CNO and inflammatory bowel disease (IBD), shedding light on shared pathophysiological mechanisms and clinical management. A thorough literature review was conducted, encompassing 24 case reports involving 40 patients. The demographic distribution of patients revealed a near-equal gender ratio, with a median age of diagnosis at 12 years. The diagnosis patterns showed a higher proportion of CNO as the initial diagnosis, while Crohn's disease was more prevalent than ulcerative colitis. The time interval between the clinical presentations varied, ranging from simultaneous detection to a substantial 15-year gap. Treatment modalities included nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, aminosalicylates, and biologic agents, such as infliximab, often overlapping in their use and suggesting shared pathophysiological pathways. Both conditions displayed systemic manifestations, and patients often responded well to immunosuppressive medications. The pathophysiology of CNO involves a genetic predisposition, cytokine dysregulation, and osteoclast activation. Dysregulated innate immunity results in immune cell infiltration into bones, causing sterile bone lesions. Notably, emerging evidence hints at a potential link between the microbiome and CNO. In contrast, IBD results from imbalanced mucosal immune responses to the intestinal microbiota. Polymorphisms in the promotor region of IL-10, common cytokines, immune cells, and genetic markers indicate shared immunological and genetic factors between CNO and IBD. Both conditions also involve extraintestinal symptoms. This analysis underscores the need for clinical awareness of the co-occurrence of CNO and IBD, especially among pediatric patients. A deepened understanding of the connections between these seemingly distinct diseases could lead to more effective management and improved patient outcomes.

Immunological Characterization of Chronic Nonbacterial Osteomyelitis (CNO) in Adults: A Cross-Sectional Exploratory Study

Chronic nonbacterial osteomyelitis (CNO) is a rare disease spectrum affecting children and adults. Adult CNO may occur as isolated bone inflammation, or with a broad range of extraskeletal features. CNO pathophysiology, including the key drivers of inflammation, remains largely unknown. For pediatric CNO, a role for pro-inflammatory cytokine dysregulation has been proposed, but studies in adults are scarce. We therefore provide immunological characterization of adult CNO. Cross-sectional study in our referral center including adult CNO patients (n = 172) and healthy controls (n = 65). Inflammation parameters and systemic inflammatory based scores(SIBS, including neutrophil/lymphocyte ratio [NLR] and systemic immune inflammation index [SII]) were compared between groups. Cytokine expression was explored with electrochemiluminescent immunoassays in 33 patients, eight healthy controls and 21 osteoporosis patients. Routine inflammation markers were higher in patients than in controls, but generally remained within reference range. Systemic inflammation was more pronounced in patients with additional vertebral involvement as compared to those osteitis in the anterior chest wall alone, in patients with comorbid pustulosis palmoplantaris or psoriasis, and in patients with strongly rather than moderately increased lesional uptake on nuclear imaging. SII was elevated in CNO patients too, but NLR was not. Cytokine expression was generally nondifferential between patients and both control groups, and patients displayed low absolute concentrations of pro-inflammatory cytokines. In this adult CNO cohort, systemic inflammation was generally subtle, but more pronounced in patients with vertebral lesions, associated skin disease, and strongly increased uptake on nuclear imaging. SII was increased in patients compared to healthy controls. Contrasting pediatric studies, we found no increased expression of the pro-inflammatory cytokines that have been proposed to drive the inflammatory cascade, like interleukin-6, -8, and -17 (IL-6, IL-8, and IL-17), and tumor necrosis α (TNF-α). Further studies are needed to evaluate the use of SII in diagnosis and monitoring of CNO, and elucidate the role of cytokine dysregulation in adult disease. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Chronic Recurrent Multifocal Osteomyelitis: A Comprehensive Literature Review

Chronic recurrent multifocal osteomyelitis (CRMO) is a non-infectious, inflammatory disorder of the bones. CRMO typically affects children, with a predisposition to females. Bone-related pain is often felt in the metaphysis of long bones, particularly of the lower extremities, but it can also target other sites at varied time intervals. Patients are likely to complain of tenderness and swelling that may cause considerable disability and adversely impact quality of life. There are three main pathophysiological mechanisms that have been hypothesized to drive CRMO including imbalanced cytokine expression, increased inflammasome activation, and enhanced osteoclast differentiation. Therapies have been based on targeting and suppressing these key players in CRMO patients. The first step in management involves pain control. Non-steroidal anti-inflammatory drugs should provide initial relief, albeit temporarily. It is imperative to initiate immunosuppressive medication that will help limit bone involvement and thereby prevent the development of fractures or leg-length discrepancies, for example. The purpose of this literature review is to study the pathophysiology of CRMO and carefully dissect the agents that have been previously employed in the management of CRMO patients. This could allow for the purposeful formulation of individualized care plans and improving the overall well-being of patients. The authors included a multitude of PubMed-indexed articles published from 2000 onwards in this review.

Classification and management strategies for paediatric chronic nonbacterial osteomyelitis and chronic recurrent multifocal osteomyelitis

INTRODUCTION

Chronic non-bacterial osteomyelitis (CNO) is an autoinflammatory bone disease that most commonly affects children and adolescents causing significant pain and damage to bones. The absence of diagnostic criteria and biomarkers, an incomplete understanding of the molecular pathophysiology, and lack of evidence from randomized and controlled trials make the diagnosis and care challenging.

AREAS COVERED

This review provides an overview of the clinical and epidemiological features of CNO and displays diagnostic challenges and how they can be addressed following strategies used internationally and by the authors. It summarizes the molecular pathophysiology, including pathological activation of the NLRP3 inflammasome and IL-1 secretion, and how these observations can inform future treatment strategies. Finally, it provides a summary of ongoing initiatives aiming at classification criteria (ACR/EULAR) and outcome measures (OMERACT) that will enable the generation of evidence through clinical trials.

EXPERT OPINION

Scientific efforts have linked molecular mechanisms to cytokine dysregulation in CNO, thereby delivering arguments for cytokine blocking strategies. Recent and ongoing collaborative international efforts are providing the basis to move toward clinical trials and target directed treatments for CNO that find approval by regulatory agencies.

Pediatric musculoskeletal infections

PURPOSE OF REVIEW

The aim of this article is to review the recent guidelines and literature regarding the diagnosis and the treatment of common pediatric musculoskeletal infections: septic arthritis, osteomyelitis, pyomyositis, and Lyme disease.

RECENT FINDINGS

In the last decade, a better understanding of the causative organisms of common bacterial infections, including Kingella , leads to prompt targeted antimicrobial coverage in all musculoskeletal infections. Prompt diagnosis and treatment continues to be the mainstay in the treatment of children with osteoarticular infections. Efforts to improve early detection have lead to improving rapid lab diagnostic testing; however, more advanced diagnostics such as arthrocentesis for septic arthritis and MRI for osteomyelitis and pyomyositis, remain the gold standard. Shorter and narrowed antibiotic courses, with appropriate transition to outpatient oral treatment provide effective infection clearance and reduction in complications of disease.

SUMMARY

Advances in diagnostics, including pathogen identification as well as imaging continues to improve our ability to diagnose and treat these infections, although still lack ability to provide definitive diagnosis without more invasive nor advanced techniques.

Gathering expert consensus to inform a proposed trial in chronic nonbacterial osteomyelitis (CNO)

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease that primarily affects children and adolescents. CNO is associated with pain, bone swelling, deformity, and fractures. Its pathophysiology is characterized by increased inflammasome assembly and imbalanced expression of cytokines. Treatment is currently based on personal experience, case series and resulting expert recommendations. Randomized controlled trials (RCTs) have not been initiated because of the rarity of CNO, expired patent protection of some medications, and the absence of agreed outcome measures. An international group of fourteen CNO experts and two patient/parent representatives was assembled to generate consensus to inform and conduct future RCTs. The exercise delivered consensus inclusion and exclusion criteria, patent protected (excludes TNF inhibitors) treatments of immediate interest (biological DMARDs targeting IL-1 and IL-17), primary (improvement of pain; physician global assessment) and secondary endpoints (improved MRI; improved PedCNO score which includes physician and patient global scores) for future RCTs in CNO.

Chronic Nonbacterial Osteomyelitis and Inflammatory Bowel Disease: A Literature Review-Based Cohort

Background: Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory bone disorder that mainly involves children and adolescents. The association with other inflammatory disorders, such as inflammatory bowel disease (IBD), psoriasis, and arthritis, has been reported in the literature. In particular, the relationship between bone and intestinal inflammation is still poorly understood. For this purpose, our review aims to describe the cases reported in the literature concerning this association and to compare them with data from our single-center cohort of patients. Methods: We conducted a literature review of published cases of CNO associated with IBD. Eligible articles were identified through a Medline search in the PubMed database until December 2022. We retrospectively reviewed medical records of patients with CNO referred to G. Pini Hospital and compared them with the literature-review-based cohort. Results: Fifty-seven patients with a defined diagnosis of CNO and associated IBD were described in the literature (female 55%). The median age of onset of the disease (CNO or IBD) was 11 years. In 32/53 (60%), a diagnosis of Crohn’s disease (CD) was made, while 18 (34%) patients were classified as suffering from ulcerative colitis (UC) and 3 (6%) from undifferentiated IBD. The diagnosis of CNO preceded the diagnosis of IBD in 59% of cases; while in 24%, IBD anticipated CNO; and in 17%, the two conditions appeared simultaneously. The median time between the two events was 24 months. In our Italian cohort (n = 23 patients), no diagnosis of IBD was made. No significant differences were found when comparing clinical and demographical characteristics of the Italian vs. review-based cohort, except for a significant involvement of rachis in the Italian group. Conclusions: The correlation between autoinflammatory bone disease and intestinal inflammation should be further investigated. It is essential to promote awareness among pediatric rheumatologists and gastroenterologists about this possible association to facilitate the diagnosis and better optimize treatment.

Clinical characteristics and predictors for recurrence in chronic nonbacterial osteomyelitis: a retrospective multicenter analysis

Background/aim

Chronic nonbacterial osteomyelitis (CNO) is a rare disease of unknown etiology and most commonly occurs during childhood or adolescence. The purpose of this study is to collect data on the clinical features, outcomes, and management of the disease and to identify the factors affecting recurrence.

Materials and methods

This is a retrospective multicenter cross-sectional study of pediatric patients diagnosed with CNO. A total of 87 patients with a diagnosis of CNO followed for at least 6 months in 8 pediatric rheumatology centers across the country between January 2010 and December 2021 were included in this study.

Results

The study included 87 patients (38 girls, 49 boys; median age: 12.5 years). The median follow-up time was 20 months (IQR: 8.5-40). The median time of diagnostic delay was 9.9 months (IQR: 3-24). Arthralgia and bone pain were the most common presenting symptoms. Multifocal involvement was detected in 86.2% of the cases and a recurrent course was reported in one-third of those included in the study. The most commonly involved bones were the femur and tibia. Vertebrae and clavicles were affected in 19.5% and 20.6% of cases, respectively. The erythrocyte sedimentation rate (ESR) values of 60.9% of the patients were above 20 mm/h and the C-reactive protein values of 44.8% were above 5 mg/L. The remission rate was 13.3% in patients using nonsteroidal antiinflammatory drugs and 75.0% in those using biological drugs. Vertebral and mandibular involvement and high ESR values at the time of diagnosis were associated with recurrence.

Conclusion

In this multicenter study, CNO with vertebral and mandibular involvement and high ESR at diagnosis were associated with recurrence.