Nail-patella syndrome is an autosomal dominant disorder caused by a mutation in the gene for the transcription factor LMX1B, which plays an important role in vertebrate limb and kidney development.
There is bilateral hypoplasia or absence of the patella, subluxation of the radial head at the elbows, and bilateral accessory iliac horns. Fingernails and toenails are absent or hypoplastic, with pitting and ridges.
Renal dysfunction occurs in up to 50% of patients due to focal segmental glomerular deposits of IgM and C3. Proteinuria, hypertension, and hematuria are the most common manifestations, but about 30% of patients with renal involvement slowly progress to renal failure.
Diagnosis of nail-patella syndrome is suggested clinically; sometimes renal biopsy and bone x-rays are indicated, which are diagnostic.
LMX1B mutation analysis is possible, including for prenatal diagnosis, but the type of mutation does not usually predict clinical severity. LMXB1 mutations affecting only the kidney have been described.
There is no specific treatment for nail-patella syndrome, but proteinuria and hypertension can be treated with ACE inhibitors.
When indicated, kidney transplantation has been successful without evidence of recurrent disease in the graft.