This disorder is a common cause of ESRD in younger individuals. It is associated with almost universal progression to ESRD. The childhood type—juvenile nephronophthisis—is an autosomal recessive disorder caused by mutations in any one of 20 NPHP genes; the type appearing in adulthood—medullary cystic disease—is autosomal dominant. Both types are manifested by multiple small renal cysts at the corticomedullary junction and medulla. The cortex becomes fibrotic, and as the disease progresses, interstitial inflammation and glomerular sclerosis appear.
Patients with both forms exhibit polyuria, pallor, and lethargy. Hypertension occurs at the later stages of disease. The juvenile form causes growth retardation and ESRD before age 20 years. Patients require large amounts of salt and water as a result of renal salt wasting. Ultrasound and CT scan show small, scarred kidneys, and an open kidney biopsy may be necessary to recover tissue from the corticomedullary junction.
There is no current medical therapy that will prevent progression to renal failure. Adequate salt and water intake are essential to replenish renal losses.