Isoform 1 and isoform 2 are widely expressed, with isoform 1 being more abundant.
Defects in XPNPEP3 are the cause of nephronophthisis-like nephropathy type 1 (NPHPL1) [MIM:613159]. A disorder with features of nephronophthisis, a cystic kidney disease leading to end-stage renal failure. Nephronophthisis is histologically characterized by modifications of the tubules with thickening of the basement membrane, interstitial fibrosis and, in the advanced stages, medullary cysts. Typical clinical manifestation are chronic renal failure, anemia, polyuria, polydipsia, isosthenuria, and growth retardation. Associations with extrarenal symptoms are frequent. In NPHPL1 patients, extrarenal symptoms include hypertension, essential tremor, sensorineural hearing loss and gout. Severely affected individuals can manifest a mitochondrial disorder with isolated complex I deficiency activity in muscle, seizures, mental retardation and hypertrophic dilated cardiomyopathy.