Larsen syndrome is a genetic disorder that causes abnormalities in bone development. Features can vary, even within the same family, and are typically seen at birth (congenital). These features may include inward and upward turned feet (club feet), dislocation of hips, knees, and elbows, extra small bones in wrists and ankles, and blunt square shaped fingertips. Affected individuals are typically shorter than their relatives (short stature), have a large range of joint movement (hypermobility) and can have an abnormal curvature of the spine (scoliosis) that may cause weakness in the limbs. Larsen syndrome may cause unique facial features, including a prominent forehead, a flattened nose, and wide set eyes. Additional features may include an opening in the roof of the mouth (cleft palate), hearing loss, or breathing problems.
Larsen syndrome is caused by a change (mutation) in the FLNB gene, which acts as an instruction for the body to make a protein that is important for bone development in the fetus. Most cases of Larsen syndrome are inherited in an autosomal dominant way, which means a mutation in one of the two copies of the FLNB gene a person has is enough to cause the condition. However, some cases of Larsen syndrome are inherited in an autosomal recessive way, which means a mutation in both copies of the FLNB gene is needed to cause the condition.
The diagnosis of Larsen syndrome is considered in a baby who has congenital bone abnormalities, which are usually noticed with a physical exam. The doctor may order imaging tests, such as a skeletal x-ray, to look for clues of the diagnosis. Genetic testing is used to confirm the diagnosis. There is no cure for Larsen syndrome. However, affected individuals can usually live into adulthood. Depending on the features of the condition, treatment may include therapies or surgery. If your child has been diagnosed with Larsen syndrome, talk with their doctor about all treatment options.