Nail-patella syndrome is caused by a mutation of a gene that plays an important role in the development of limbs and kidneys.
Commonly, people who have this syndrome are missing one or both kneecaps (patellas), have an arm bone (radius) that is dislocated at the elbow, and have an abnormally shaped pelvic bone. Their fingernails and toenails are missing or poorly developed, with pitting and ridges.
About 50% of people with this syndrome have blood in their urine (hematuria) or protein in their urine (proteinuria). Kidney failure eventually develops in about 30% of the people with affected kidneys by the time they are 50 or 60. People who have kidney problems often have high blood pressure (hypertension).
The diagnosis of nail-patella syndrome is suggested by the symptoms and results of a physical examination and is confirmed by bone x-rays and a biopsy of kidney tissue (removal of a tissue sample for examination under a microscope). Genetic testing also can be done.
People who have blood or protein in their urine may undergo kidney function tests.
There is no effective treatment for nail-patella syndrome.
Controlling high blood pressure and protein in the urine with drugs called angiotensin-converting enzyme (ACE) inhibitors may slow the rate at which kidney function deteriorates. People who develop kidney failure need dialysis or a kidney transplant.
Genetic testing should be offered to people who want to have children.