Case Report: SAPHO Syndrome Mimicking Bone Metastases During Treatment With Pembrolizumab for Non-small Cell Lung Cancer

Therapeutic approaches for SAPHO syndrome from the perspective of pathogenesis: a review of the literature

Synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome is a rare autoinflammatory disease characterized by cutaneous manifestations and osteoarticular damage. The pathogenesis of SAPHO syndrome has not yet been elucidated, but studies have shown that the abnormal bone metabolism of patients with SAPHO syndrome is most likely due to localized infections that induce immune disorders in the body. Although no standardized treatment protocols exist, based on existing case studies and data from open studies, we propose that the treatment of SAPHO syndrome can be categorized into three areas according to the symptomatic manifestations of the disease: (1) control of focal infections using antibiotics and tonsillectomy; (2) administration of DMARDs to manage disease progression; and (3) bone remodeling therapy with bisphosphonates to address abnormal bone metabolism. Furthermore, a comprehensive treatment approach tailored to the clinical manifestations of the patient can effectively alleviate symptoms and enhance quality of life.

The knowledge and skills required for the onco-rheumatologist: Study of four-year consultation records of a high-volume cancer centre

OBJECTIVES

Onco-rheumatology, the intersection of oncology and rheumatology, is an emerging field requiring further definition. This study aimed to identify the knowledge and skills essential for rheumatologists in clinical oncology.

METHODS

We retrospectively reviewed consultations with the onco-rheumatology department of a high-volume tertiary cancer centre in Japan from January 2020 to December 2023.

RESULTS

We analysed 417 consultations. The most common consultation (229, 55%) was related to immune checkpoint inhibitor-induced immune-related adverse events (irAEs). Of the 238 irAEs in 185 patients, 15% were rheumatic and 85% were nonrheumatic (e.g. hepatobiliary toxicities, colitis). Approximately 25% of nonendocrine irAEs were refractory/relapsing, requiring second-line therapy (e.g. mycophenolate mofetil, biologics, immunoglobulin). In addition to irAE consultations, 137 (33%) consultations were about possible rheumatic diseases. The final diagnosis often related to cancer treatment, such as granulocyte colony-stimulating factor-related aortitis (15 patients, 11%), olaparib-related erythema nodosum (10 patients, 7.3%), and surgical menopause-related arthralgia (10 patients, 7.3%). Five patients (3.6%) were diagnosed with autoinflammatory bone disease mimicking bone tumours.

CONCLUSIONS

Onco-rheumatologists are expected to play a central role in the management of a wide range of irAEs, not limited to rheumatic irAEs. They must also manage rheumatologic manifestations during cancer treatment and rheumatic diseases that mimic tumours.

Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis (SAPHO) Syndrome Mimicking Bone Metastases in the Spine: A Presentation of Two Cases and Literature Review

Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is a rare disorder of unknown etiology with heterogeneous clinical manifestations. We describe two cases of patients diagnosed with SAPHO syndrome mimicking spinal bone metastases. A literature review was conducted to identify similar previously reported cases. The first patient was a 56-year-old woman with progressive back pain for six months who was referred to the neurosurgery department for suspected spinal metastases. A spinal CT scan revealed hyperdense lesions at T10 and hyperdense changes in the lumbar vertebrae. Spinal MRI demonstrated bone marrow edema that was hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging in multiple thoracic vertebrae, and the PET/CT showed multiple skeletal lesions affecting the spine with low-to-moderate 18F-FDG uptake. Scintigraphy showed the characteristic "bull's head" sign with increased uptake in the manubrium and bilateral sternoclavicular joints. The second patient was a 66-year-old woman with a four-month history of back pain, who was admitted with multiple spinal lesions. The diagnosis was made after bone scintigraphy demonstrated the characteristic findings of the syndrome. Both patients lacked cutaneous lesions on presentation but reported previous skin lesions. SAPHO syndrome is a rare condition, and bone lesions associated with the disease may be misdiagnosed as bone metastases. Knowledge of the syndrome and its imaging findings is essential for accurate diagnosis and treatment.

Acne Syndromes and Mosaicism

Abnormal mosaicism is the coexistence of cells with at least two genotypes, by the time of birth, in an individual derived from a single zygote, which leads to a disease phenotype. Somatic mosaicism can be further categorized into segmental mosaicism and nonsegmental somatic mosaicism. Acne is a chronic illness characterized by inflammatory changes around and in the pilosebaceous units, commonly due to hormone- and inflammatory signaling-mediated factors. Several systemic disorders, such as congenital adrenal hyperplasia, polycystic ovarian syndrome, and seborrhoea-acne-hirsutism-androgenetic alopecia syndrome have classically been associated with acne. Autoinflammatory syndromes, including PAPA, PASH, PAPASH, PsAPASH, PsaPSASH, PASS, and SAPHO syndromes include acneiform lesions as a key manifestation. Mosaic germline mutations in the FGFR2 gene have been associated with Apert syndrome and nevus comedonicus, two illnesses that are accompanied by acneiform lesions. In this review, we summarize the concept of cutaneous mosaicism and elaborate on acne syndromes, as well as acneiform mosaicism.