Medullary cystic kidney disorder is a familial disorder that is progressive in nature and results in renal failure. Historically believed to be the same disorder, nephrophthisis (NPH), the autosomal recessive form of medullary cystic disease, is more likely to become evident in late adolescence, and therefore males and females are affected equally. There is also a form of medullary cystic disease that is autosomal dominant. Medullary cystic kidney disorder occurs in 2 in 100,000 individuals and usually is not evident until adulthood. There is considerable genetic variability of gene loci, and recent research suggests that NPH and medullary cystic disorder may involve different genetic loci. Despite the differences, NPH and medullary cyctic disease are often grouped together and share similar presentation. Both forms are evident across ethnic groups.