Figure 948

Nephronophthisis (NPH): renal involvement. Kidney biopsy specimen visualized by light microscopy with periodic acid-Schiff stain, in a patient with juvenile NPH of an early stage. Note the typical thickening and disruption of the tubular basement membrane (appearing in red); the histiolymphocytic infiltration present at this stage is progressively replaced by interstitial fibrosis.

NPH is an autosomal recessive disorder, accounting for 10% to 15% of all children admitted for end-stage renal failure. Although classified as a renal cystic disorder, NPH is characterized by chronic diffuse tubulointerstitial nephritis; the presence of cysts at the corti-comedullary boundary (thus, the alternative term "medullary cystic disease," now preferably reserved for the autosomal-dominant form; see Fig. 9-43) is a late manifestation of the disease. Clinical features include early polyuria-polydypsia, unremarkable urinalysis, frequent absence of hypertension, and eventually, end-stage renal failure at a median age of 13 (range 3 to 23) years. Ultrasonographic features are summarized in Figure 9-2; medullary cysts are sometimes detected. Associated disorders are detailed in Figure 9-49. A gene called NPH1 that has been identified on chromosome 2 accounts for about 80% of cases [41, 42]. In two thirds of them, a large homozygous deletion is detected in this gene [43]. (Courtesy of P. Niaudet.)

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