Nephronophthisis is characterized by the development of cysts at the corticomedullary junction, in association with chronic tubulointerstitial nephritis, and is distinguished from other medullary cystic disorders (such as Senior-Loken syndrome and autosomal recessive polycystic kidney disease) in that nephronophthisis has a purely renal pathophysiology. Juvenile nephronophthisis (NPH1) presents late in the first decade of life. This autosomal recessive disorder has been mapped to chromosome 2q13, and recent molecular studies have identified, at this locus, a gene (NPHP1) that is involved in most cases of NPH1. Reports described a group of infants who reached end stage renal disease (ESRD) before 2 years of age, with chronic tubulointerstitial nephritis that had pathological features similar to juvenile nephronophthisis. This disorder has been designated "infantile nephronophthisis" (NPH2).