Fibrodysplasia Ossificans

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic progressive disorder that affects humans and animals. In dogs and cats, the disorder is marked by proliferation of fibrovascular tissue within a muscle occurs with subsequent calcification and ossification (chronic, painful wounds and calcified deposits in the paws and abdomen). The disorder typically affects young and middle-aged animals of both sexes. Clinical signs include progressive weakness and stiffness of gait, enlargement of limb muscles and muscle pain and visible limb swelling, marked atrophy of the muscles, and limited mobility of all joints. Since it is a progressive disorder, the prognosis is guarded to poor. Inheritance of the disorder has not yet been demonstrated.

Fibrodysplasia Ossificans Progressiva in Humans

Fibrodysplasia ossificans progressiva (FOP) is the most catastrophic disorder of heterotopic ossification in humans. Throughout childhood and early adult life, FOP progressively immobilizes all of the joints of the normotopic skeleton, rendering movement impossible. Any small injury to connective tissue (muscles, ligaments, and tendons) can result in the formation of hard bone around the damaged site. Children are born with a characteristic malformation of the great toes and begin to develop heterotopic (extra) bone formation during early childhood. Eventually, a second skeleton begins to form that severely restricts mobility.

Causes of Fibrodysplasia Ossificans Progressiva

FOP is associated with dysregulated production of bone morphogenetic protein 4 (BMP4). BMPs play an important role in the growth and development of numerous tissues, including bone, brain, and spinal cord.

Treatment of Fibrodysplasia Ossificans Progressiva

At present, there is no effective prevention or treatment. The recent discovery of the FOP gene establishes a critical milestone in understanding FOP, reveals a target for drug development.

References:
1. A Practical Guide to Canine and Feline Neurology. Curtis W. Dewey 2. Fibrodysplasia ossificans progressiva-like condition in a cat.Asano K, Sakata A, Shibuya H, Kitagawa M, Teshima K, Kato Y, Sasaki Y, Kutara K, Seki M, Edamura K, Sato T, Tanaka S.