Nail-patella syndrome

Nail-patella syndrome is a rare inherited disorder caused by mutations in the LMX1B gene, passed on in an autosomal dominant pattern, meaning a single altered copy from one parent is enough to cause the condition. It takes its name from its two most common features: poorly developed or absent fingernails, most noticeable on the thumbs, affecting about 95 percent of patients, and underdeveloped or missing kneecaps, affecting about 75 percent. A distinctive diagnostic clue is triangular rather than the usual rounded lunulae, the pale half-moons at the base of the fingernails. Because LMX1B also guides development elsewhere in the body, the syndrome can affect the elbows, hips, chest and other joints, and it carries meaningful risk to the kidneys, including proteinuria and nephritis that can progress to kidney disease, and to the eyes, including a predisposition to open-angle glaucoma. Older names for the same condition include iliac horn syndrome, hereditary onychoosteodysplasia, Fong disease and Turner-Kieser syndrome.