Fibrodysplasia ossificans progressiva
Citation, DOI & article data
Fibrodysplasia ossificans progressiva (FOP), previously known as myositis ossificans progressiva (MOP) and also known as Munchmeyer disease, is a rare, inherited disorder characterized by progressive fibrosis and ossification of muscles, tendons, fasciae, aponeuroses, and ligaments of multiple sites. It is disabling and ultimately fatal.
Fibrodysplasia ossificans progressiva should not be confused with myositis ossificans circumscripta, which is usually post-traumatic.
Fibrodysplasia ossificans progressiva is a very rare disease, with an estimated prevalence of ~1 per 2 million. There is no racial/ethnic, or gender predilection 3. The process and symptoms of heterotopic ossification start between 2 and 5 years old.
Most cases arise from sporadic mutations, although some are inherited in an autosomal dominant fashion 3.
Fibrodysplasia ossificans progressiva can be evaluated using plain radiographs, CT and/or MRI. MRI is mostly useful for more subtle edema which would not be seen on the other modalities. Characteristic features include:
- congenital hallux valgus
- monophalangic first toe
- shortened metacarpals
- pseudoexostoses (ossification of ligamentous insertions)
- microdactyly of the first metacarpal/metatarsal
- neck muscle edema
- C2-C7 facet joint fusion
- enlarged vertebrae 4
Treatment and prognosis
This is a progressive, fatal disease with the median survival being 45 years.
Since the process of heterotopic ossification is quite unique, differential diagnosis on a long term basis is quite limited. However, for punctual abnormalities, the following differential diagnosis should be considered:
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- 2. Fisher D & Hinke M. Musculoskeletal Case of the Day. AJR Am J Roentgenol. 1986;146(5):1087-93. doi:10.2214/ajr.146.5.1087 - Pubmed
- 3. Kaplan F, Le Merrer M, Glaser D et al. Fibrodysplasia Ossificans Progressiva. Best Pract Res Clin Rheumatol. 2008;22(1):191-205. doi:10.1016/j.berh.2007.11.007 - Pubmed
- 4. Kumar R, Guinto F, Madewell J, Swischuk L, David R. The Vertebral Body: Radiographic Configurations in Various Congenital and Acquired Disorders. Radiographics. 1988;8(3):455-85. doi:10.1148/radiographics.8.3.3380991 - Pubmed