Nephronophthisis is a chronic tubulointerstitial nephropathy that progresses to end-stage renal failure. Prevalence is 1/100 000 individuals. The disease is both clinically and genetically heterogeneous. Three main clinical forms have been described. Juvenile nephronophthisis, the most frequent form, progresses to end-stage renal failure before the age of 15 and is responsible for 15% of cases of childhood end-stage renal failure. The first signs appear after the age of 2 with a urine concentration defect responsible for polyuria and polydipsia, failure to thrive and a progressive deterioration of renal function without signs of glomerular disease. Renal ultrasonography reveals normal-sized kidneys. Histological lesions affect the tubular basement membranes, which are irregularly thickened and multilayered, or thinned. Interstitial fibrosis is also present. Some children present with extrarenal symptoms: tapetoretinal degeneration (as in Senior-Loken syndrome, see this term), intellectual deficiency, cerebellar ataxia, bone anomalies or liver involvement. Infantile nephronophthisis is a chronic tubulointerstitial nephropathy with cortical microcysts progressing to end-stage renal failure before age 5. Finally, the late-onset form of nephronophthisis is a rarer form of the disease. Clinical and histological signs are similar to those of the juvenile form, but the age at which renal failure reaches a terminal stage occurs later than in the juvenile form, at a mean age of 19 years. Nephronophthisis is inherited in an autosomal recessive manner and five genes associated with the disease have been identified. The first gene, NPHP1, has been mapped to chromosome 2q13. Homozygous deletions have been observed in 70% of affected children and their detection by PCR allows the diagnosis to be established. The existence of genetic heterogeneity has been shown in patients with or without extra-renal involvement. Mutations in the NPHP2 gene, coding for inversin, are responsible for the infantile form of nephronophthisis, which progresses to end-stage renal failure before the age of 5 years. Mutations of the NPHP3 gene, localised to chromosome 3q21-22, have been described in a large Venezuelan family and cause the late-onset form of the disease. Mutations of the NPHP4 gene, localised to chromosome 1p36 have been observed in several families, some of which had associated retinal involvement. Mutations of another gene, IQCB1/NPHP5, localised to chromosome 3q13, have recently been identified in patients with autosomal recessive nephronophthisis and Senior-Loken syndrome. Antenatal diagnosis can be performed when the mutation has been identified in one child of the family. At present, there is no treatment for preventing progression to end-stage renal failure.
Last update: February 2007