Nail-patella syndrome (NPS) is a genetic disorder that is also known as Iliac Horn Syndrome. Nail-patella syndrome is a connective tissue that produces defects in the fingernails, knee caps, and kidneys. It is caused by mutations in a gene known as LIM Homeobox Transcription Factor 1-Beta (LMX1B), located on the long arm of chromosome 9. Nail abnormalities are seen in almost all individuals with nail-patella syndrome. The nails may be absent or underdeveloped and discolored, split, ridged, or pitted. The fingernails are more likely to be affected than the toenails, and the thumbnails are usually the most severely affected.
In many people with this condition, the areas at the base of the nails (lunulae) are triangular instead of the usual crescent shape. Some people with this condition may not be capable to fully expand their arms or turn their palms up while keeping their elbows straight. The elbows may also be angled outward (cubitus valgus) or have abnormal webbing. Many individuals with nail-patella syndrome have horn-like outgrowths of the iliac bones of the pelvis (iliac horns). These abnormal projections may be felt through the skin, but they do not cause any symptoms and are usually detected on a pelvic x-ray.
Iliac horns are very common in people with nail-patella syndrome and are rarely, if ever, seen in people without this condition.Various skeletal symptoms may occur. Other areas of the body may also be affected in nail-patella syndrome, particularly the eyes and kidneys. Some people develop kidney disease, which can progress to kidney failure. Kidney failure is the most dangerous consequence of nail-patella syndrome. It occurs in about 30% of patients who have kidney involvement. Eye problems may be present and vary from person to person. Nail-patella syndrome is associated with open angle glaucoma.
Treatment is usually not necessary. Treatment, when required, depends on each patient’s specific symptoms. Severe kidney disease is treated with dialysis or a kidney transplant. Renal transplantation has proven successful in patients with nail-patella syndrome (NPS) who develop ESRD. A wheelchair may be required if walking becomes painful due to bone, tendon, ligament, or muscle defects. Genetic counselling should be offered to all individuals with NPS. Orthopedic surgery may be necessary for congenital clubfoot deformity. Manipulation or surgery may be required to correct hip dislocation. Cataracts are also surgically treated.