Larsen syndrome

Larsen syndrome is a congenital disorder first described in 1950 by Larsen and his associates, who saw dislocation of the large joints together with facial abnormalities in six patients. Typical features include dislocated knees, hips and elbows, a flattened face, a prominent forehead and a depressed nasal bridge, and it can also bring cardiovascular and orthopedic abnormalities. It is linked to a defect in the gene for filamin B, a cytoplasmic protein that helps regulate the structure and activity of the cytoskeleton, and it has been described as a mesenchyme disorder affecting connective tissue. Both autosomal dominant and recessive forms have been reported, most cases being dominant. In Western populations about one birth in 100,000 is affected, a figure probably too low because the disorder is often unrecognised or misdiagnosed.