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Bernard J Smilde,1– 3 Esmée Botman,1– 3 Ruben D de Ruiter,1– 3 Jan Maerten Smit,2,4 Berend P Teunissen,2,5 Wouter D Lubbers,2,6 Lothar A Schwarte,2,6 Patrick Schober,2,6 E Marelise W Eekhoff1– 3 1Amsterdam UMC Location Vrije Universiteit Amsterdam, Department of Internal Medicine Section Endocrinology, Amsterdam, the Netherlands; 2Amsterdam UMC, Amsterdam Bone Center, Amsterdam, the Netherlands; 3Amsterdam Movement Sciences, Tissue Function and Regeneration, Amsterdam, the Netherlands; 4Amsterdam UMC Location Vrije Universiteit Amsterdam, Department of Plastic, Reconstructive and Hand Surgery, Amsterdam, the Netherlands; 5Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Radiology and Nuclear Medicine, Amsterdam, the Netherlands; 6Amsterdam UMC Location Vrije Universiteit Amsterdam, Department of Anaesthesiology, Amsterdam, the NetherlandsCorrespondence: E Marelise W Eekhoff, Department of Internal Medicine section Endocrinology, Amsterdam UMC location Vrije Universiteit Amsterdam, De Boelelaan 1117, Amsterdam, the Netherlands, Tel +31 204440588, Email emw.eekhoff@amsterdamumc.nlAbstract: Fibrodysplasia ossificans progressiva (FOP), sometimes known as myositis ossificans progressiva, is an ultra-rare disease in which bone is formed in muscular tissue, tendons and ligaments. This is known as heterotopic ossification (HO). FOP is caused by a heterozygous mutation in the highly conserved ACVR1/ALK2 gene which affects about 1 in 1.5– 2 million individuals. At birth, patients with the predominant R206H mutation only exhibit a bilateral hallux valgus. During childhood, heterotopic bone formation develops in a typical pattern, affecting the axial muscles first before appendicular body parts are involved. HO can start spontaneously but is often elicited by soft tissue trauma or medical procedures. After soft tissue injury, an inflammatory process called a flare-up can start, followed by the formation of HO. HO leads to a limited range of motion, culminating in complete ankylosis of nearly all joints. As a result of HO surrounding the thorax, patients often suffer from thoracic insufficiency syndrome (TIS). TIS is the most common cause of a limited life expectancy for FOP patients, with a median life expectancy of 56 years. Management is focused on preventing soft-tissue injury that can provoke flare-ups. This includes prevention of iatrogenic damage by biopsies, intramuscular injections and surgery. Anti-inflammatory medication is often started when a flare-up occurs but has a poor basis of evidence. Several forms of potential treatment for FOP are being researched in clinical trials. Progression of the disease is monitored using CT and 18F-NaF PET/CT combined with functional assessments. Patients are regularly evaluated for frequently occurring complications such as restrictive lung disease. Here, we review the current management, monitoring and treatment of FOP.Keywords: fibrodysplasia ossificans progressiva, heterotopic ossification, activin A receptor type 1, treatment strategies |
