Myositis ossificans progressiva, also known as fibrodysplasia ossificans progressiva, is one of two kinds of heterotopic ossification or calcification of the muscle. This is a rare genetic condition, with an autosomal dominant pattern, in which the ossification occurs even without injury and grows in an often predictable pattern.

The characteristics of myositis ossificans progressiva make diagnosis simple via clinical examination and radiology alone.

There is scarce evidence that any type of treatment arrests the progress of the myositis ossificans progressiva condition. Treatments of choice include imposing a Vitamin D and calcium rich diet, the avoidance of direct sunlight, and administering of corticosteroids. Additionally, beryllium, vitamins B and E and penicillamine may also be used in treating patients. Of late, calcification-blocking drugs have been administered without any proven benefits. On the surgical side, resection of the ossified sites is usually unsuccessful, with ossification in the same areas often recurring. On occasion, however, good outcomes have been reported post-surgery.

The formation of extra-skeletal bone causes loss of mobility because the joints become affected. Patients born with myositis ossificans progressiva may have trouble opening the mouth fully, and thus are unable to speak and eat without difficulty. As the condition progresses, patients may suffer from malnutrition because of their eating difficulties. Consequently, they may also have problems breathing because extra bone forms around the rib cage and restricts normal lung expansion. Any muscle trauma (such as a fall or invasive surgery) in patients born with myositis ossificans progressiva patients may cause muscle swelling and inflammation, followed by rapid ossification in the area with injury. Such episodes may also be triggered by certain viral afflictions such as influenza. In general, people with this genetic disorder are born with big, malformed toes. The big toe abnormality is a distinguishing feature that helps identify this affliction from other bone and muscle diseases. Additionally, afflicted patients may also possess short thumbs and other visible skeletal defects.

Myositis ossificans progressiva is a congenital condition, an inherited affliction usually caused by mutations in the ACVRI gene. The ACVRI is the gene responsible for producing morphogenetic protein (BMP) type I receptors, which are found in many tissues including the skeletal muscle and cartilage. The ACVRI protein helps control the development and growth of muscles and bones. From birth to young adulthood, it is this protein family that aids in the gradual replacement of cartilage by bone ossification in the normal skeletal maturation. Myositis ossificans progressiva is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is enough to cause the condition.

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