SNP Shot: Genomic Insights

Fibrodysplasia ossificans progressiva (FOP) is a rare condition where muscles and connective tissues (tendons and ligaments) progressively turn into bone. This process, known as ossification, results in the formation of bone outside of the normal skeleton (heterotopic ossification), severely restricting movement. The condition typically manifests in early childhood, initially affecting the neck and shoulders before progressing down the body and into the limbs.

As extra bone develops, individuals with FOP experience a gradual loss of mobility as their joints become fused. Difficulty opening the mouth fully can impair speech and eating. Consequently, malnutrition can arise over time due to these eating difficulties. Furthermore, bone formation around the rib cage can restrict lung expansion, leading to breathing problems.

In individuals with FOP, any injury to the muscles, such as from falls or invasive medical procedures, can trigger episodes of muscle swelling and inflammation (myositis). This inflammation is then followed by accelerated bone formation in the affected area. Viral infections, such as influenza, can also trigger these flare-ups.

A hallmark of FOP is malformed big toes present at birth. This distinctive feature helps differentiate FOP from other bone and muscle disorders. Individuals with FOP may also exhibit short thumbs and other skeletal abnormalities.

Inheritance:

FOP is typically inherited in an autosomal dominant manner. This means that only one copy of the mutated gene in each cell is enough to cause the condition. Most cases are due to new, spontaneous gene changes. These individuals have no family history of FOP. In a small minority of cases, the altered gene is inherited from an affected parent.