Nail-Patella Syndrome (Hereditary Onychoosteodysplasia)
David R. Powell
The cardinal features of nail-patella syndrome (NPS) are dysplastic nails and hypoplastic patellae; some patients have iliac horns, knee and elbow abnormalities, cataracts, and renal disease. NPS is inherited as an autosomal dominant disorder, probably with full penetrance but with variable expressivity. Affected individuals have heterozygous mutations in the transcription factor LMX1B. Impaired development of dorsal limb structures such as nails and patellae is consistent with an essential role for LMX1B in orchestrating normal dorsal-ventral limb patterning in vertebrates.
Renal disease aggregates in some kindreds with NPS while sparing others. In kindreds with a history of nephropathy, 50% of family members develop renal disease, and 15% progress to renal failure. The presence of nephropathy or renal failure in parents with NPS does not increase the risk of the same complication developing in their children. Most patients present with proteinuria, which may lead to nephrotic syndrome; occasionally, NPS is associated with congenital nephrosis. Chronic renal failure has been reported in children younger than 10 years, but usually it develops in teenagers and young adults, sometimes after they have had asymptomatic proteinuria for years.