Fibrodysplasia ossificans progressiva. A case report and focus on the BMP signaling pathway

Pain Phenotypes in Rare Musculoskeletal and Neuromuscular Diseases

For patients diagnosed with a rare musculoskeletal or neuromuscular disease, pain may transition from acute to chronic; the latter yielding additional challenges for both patients and care providers. We assessed the present understanding of pain across a set of ten rare, noninfectious, noncancerous disorders; Osteogenesis Imperfecta, Ehlers-Danlos Syndrome, Achondroplasia, Fibrodysplasia Ossificans Progressiva, Fibrous Dysplasia/McCune-Albright Syndrome, Complex Regional Pain Syndrome, Duchenne Muscular Dystrophy, Infantile- and Late-Onset Pompe disease, Charcot-Marie-Tooth Disease, and Amyotrophic Lateral Sclerosis. Through the integration of natural history, cross-sectional, retrospective, clinical trials, & case studies we described pathologic and genetic factors, pain sources, phenotypes, and lastly, existing therapeutic approaches. We highlight that while rare diseases possess distinct core pathologic features, there are a number of shared pain phenotypes and mechanisms that may be prospectively examined and therapeutically targeted in a parallel manner. Finally, we describe clinical and research approaches that may facilitate more accurate diagnosis, monitoring, and treatment of pain as well as elucidation of the evolving nature of pain phenotypes in rare musculoskeletal or neuromuscular illnesses.

Targeting heterotopic ossification by inhibiting activin receptor‑like kinase 2 function (Review)

Heterotopic ossification (HO) refers to the appearance of osteoblasts in soft tissues under pathological conditions, such as trauma or infection. HO arises in an unpredictable way without any recognizable initiation. Activin receptor-like kinase-2 (ALK2) is a type I cell surface receptor for bone morphogenetic proteins (BMPs). The dysregulation of ALK2 signaling is associated with a variety of diseases, including cancer and HO. At present, the prevention and treatment of HO in the clinic predominantly includes nonsteroidal anti-inflammatory drugs (NSAIDs), bisphosphonates and other drug treatments, low-dose local radiation therapy and surgical resection, rehabilitation treatment and physical therapy. However, most of these therapies have adverse effects. These methods do not prevent the occurrence of HO. The pathogenesis of HO is not being specifically targeted; the current treatment strategies target the symptoms, not the disease. These treatments also cannot solve the fundamental problem of the occurrence of HO. Therefore, scholars have been working to develop targeted therapies based on the pathogenesis of HO. The present review focuses on advances in the understanding of the underlying mechanisms of HO, and possible options for the prevention and treatment of HO. In addition, the role of ALK2 in the process of HO is introduced and the progress made towards the targeted inhibition of ALK2 is discussed. The present study aims to offer a platform for further research on possible targets for the prevention and treatment of HO.

Extraskeletal Calcifications in Hutchinson-Gilford Progeria Syndrome

PURPOSE

Children with Hutchinson-Gilford progeria syndrome (HGPS), a rare premature aging disease, exhibit extraskeletal calcifications detected by radiographic analysis and on physical examination. The aim of this study was to describe the natural history and pathophysiology of these abnormal calcifications in HGPS, and to determine whether medications and/or supplements tested in clinical trials alter their development.

METHODS

Children from two successive clinical trials administering 1) lonafarnib (n = 26) and 2) lonafarnib + pravastatin + zoledronic acid (n = 37) were studied at baseline (pre-therapy), one year on therapy, and at end-of-therapy (3.3-4.3 years after the baseline visit). Calcium supplementation (oral calcium carbonate) was administered during the first year of the second trial and was subsequently discontinued. Information on calcifications was obtained from physical examinations, radiographs, and serum and urinary biochemical measures. The mineral content of two skin-derived calcifications was determined by x-ray diffraction.

RESULTS

Extraskeletal calcifications were detected radiographically in 12/39 (31%) patients at baseline. The odds of exhibiting calcifications increased with age (p = 0.045). The odds were unaffected by receipt of lonafarnib, pravastatin, and zoledronate therapies. However, administration of calcium carbonate supplementation, in conjunction with all three therapeutic agents, significantly increased the odds of developing calcifications (p = 0.009), with the odds plateauing after the supplement's discontinuation. Composition analysis of calcinosis cutis showed hydroxyapatite similar to bone. Although serum calcium, phosphorus, and parathyroid hormone (PTH) were within normal limits at baseline and on-therapy, PTH increased significantly after lonafarnib initiation (p < 0.001). Both the urinary calcium/creatinine ratio and tubular reabsorption of phosphate (TRP) were elevated at baseline in 22/39 (56%) and 31/37 (84%) evaluable patients, respectively, with no significant changes while on-therapy. The mean calcium × phosphorus product (Ca × Pi) was within normal limits, but plasma magnesium decreased over both clinical trials. Fibroblast growth factor 23 (FGF23) was lower compared to age-matched controls (p = 0.03).

CONCLUSIONS

Extraskeletal calcifications increased with age in children with HGPS and were composed of hydroxyapatite. The urinary calcium/creatinine ratio and TRP were elevated for age while FGF23 was decreased. Magnesium decreased and PTH increased after lonafarnib therapy which may alter the ability to mobilize calcium. These findings demonstrate that children with HGPS with normal renal function and an unremarkable Ca × Pi develop extraskeletal calcifications by an unidentified mechanism that may involve decreased plasma magnesium and FGF23. Calcium carbonate accelerated their development and is, therefore, not recommended for routine supplementation in these children.

Challenges in the treatment of fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP), is a rare autosomal dominant connective tissue disease with a prevalence of 1 in 2 million. It is characterized by congenital foot deformities and multiple heterotopic ossifications in fibrous tissue. It usually starts with painful soft tissue swellings occurring with attacks at the ages of three or four. The attacks develop spontaneously or after minor trauma, and gradually turn into heterotopic ossifications that cause joint limitations, growth defects, skeletal deformities and chronic pain. The average life expectancy is forthy, and most of the patients are lost due to pulmonary complications. FOP is often misdiagnosed as fibromatosis, desmoid tumour or cancer, bunion, myositis, arthritis and rheumatic diseases. After clinical suspicion, confirmatory genetic analysis should be used for the diagnosis. The treatment of FOP is currently supportive. An effective, proven method has not yet been established. Herein, we present an 18-year-old female patient with FOP who underwent different treatment modalities in a 5-year period. This case-based review reveals all available treatment approaches with at least 6-month follow-up for FOP in the literature.

Conserved signaling pathways underlying heterotopic ossification

Heterotopic ossification (HO), a serious disorder of extra-skeletal bone formation, occurs as a common complication of trauma or in rare genetic disorders. Many conserved signaling pathways have been implicated in HO; however, the exact underlying molecular mechanisms for many forms of HO are still unclear. The emerging picture is that dysregulation of bone morphogenetic protein (BMP) signaling plays a central role in the process, but that other conserved signaling pathways, such as Hedgehog (HH), Wnt/β-catenin and Fibroblast growth factors (FGF), are also involved, either through cross-talk with BMP signaling or through other independent mechanisms. Deep understanding of the conserved signaling pathways is necessary for the effective prevention and treatment of HO. In this review, we update and integrate recent progress in this area. Hopefully, our discussion will point to novel promising, druggable loci for further translational research and successful clinical applications.

Difficult diagnosis and genetic analysis of fibrodysplasia ossificans progressiva: a case report

Background

Fibrodysplasia ossificans progressiva (FOP), an ultra-rare and disabling genetic disorder of skeletal malformations and progressive heterotopic ossification, is caused by heterozygous activating mutations in activin A receptor, type I/activin-like kinase 2 (ACVR1/ALK2). The rarity of the disease makes it common to make a misdiagnosis and cause mismanagement.

Case presentation

We reported a case of a sixteen-year-old male patient who had suffered from pain and swelling in the biopsy site for two months. His physical examination presented serious stiffness and multiple bony masses in the body, with his bilateral halluces characterized by hallux valgus deformity and macrodactyly. Imaging examinations showed widespread heterotopic ossification. All laboratory blood tests were normal except for the one on alkaline phosphatase. A de novo heterozygous mutation (c.617G > A; p.R206H) were found in the ACVR1/ALK2 using gene sequencing.

Conclusion

Even though FOP is a rare disorder of genetic origin, which is generally misdiagnosed, the genetic analysis could provide definitive confirmation of the disease. Awareness of such an important approach can help clinicians to avoid the commonly practiced misdiagnosis and mismanagement of the rare disease.