A Bedouin kindred with infantile nephronophthisis demonstrates linkage to chromosome 9 by homozygosity mapping

A novel type of infantile nephronophthisis was identified in an extended Bedouin family from Israel. This disease has an autosomal recessive mode of inheritance, with the phenotypic presentation ranging from a Potter-like syndrome to hyperechogenic kidneys, renal insufficiency, hypertension, and hyperkalemia. Affected individuals show rapid deterioration of kidney function, leading to end-stage renal failure within 3 years. Histopathologic examination of renal tissue revealed variable findings, ranging from infantile polycystic kidneys to chronic tubulointerstitial nephritis, fibrosis, and cortical microcysts. A known familial juvenile nephronophthisis locus on chromosome 2q13 and autosomal recessive polycystic kidney disease on chromosome 6p21.1-p12 were excluded by genetic linkage analysis. A genomewide screen for linkage was conducted by searching for a locus inherited by descent in all affected individuals. Pooled DNA samples from parents and unaffected siblings and individual DNA samples from four affected individuals were used as PCR templates with trinucleotide- and tetranucleotide-repeat polymorphic markers. Using this approach, we identified linkage to infantile nephronophthisis for markers on chromosome 9q22-31. The disorder maps to a 12.9-cM region flanked by markers D9S280 and GGAT3G09.