fibrodysplasia ossificans progressiva

FOP is characterized by the association of skeletal abnormalities mainly in great toes, and enchondral ossifications in tendons and muscles. This rare disorder is characterized by physical handicap due to intermittently progressive ectopic ossification and malformed big toes which are often monophalangic. Occasional features include short thumbs, fifth finger clinodactyly, malformed cervical vertebrae, short broad femoral necks, deafness, scalp baldness, and mild mental retardation.

BMP dysregulation seems to be the main underlying mechanism of the heterotopic ossifications.

Etiology

 germline mutations in

• fibrodysplasia ossificans progressiva can be caused by mutation in the ACVR1 gene (MIM.102576) on chromosome 2q23.
   the NOG gene (noggin) at 17q22 (MIM.602991)
• Other loci are involved.

References

 Gannon FH, Kaplan FS, Olmsted E, Finkel GC, Zasloff MA, Shore E. Bone morphogenetic protein 2/4 in early fibromatous lesions of fibrodysplasia ossificans progressiva. Hum Pathol. 1997 Mar;28(3):339-43. PMID: 9042799