Confirmation of a gene locus for medullary cystic kidney disease (MCKD2) on chromosome 16p12

Background. Autosomal-dominant medullary cystic kidney disease (MCKD) is an interstitial nephropathy characterized by structural renal tubular defects that result in salt wasting and a reduction in urinary concentration. The condition has clinical and morphological similarities to autosomal-recessive juvenile nephronophthisis. Two genes predisposing to MCKD have been localized. MCKD1 on chromosome lq21 was localized in two Cypriot families, and MCKD2 on chromosome 16p12 was localized in a single Italian family. We have evaluated a large Welsh MCKD family for linkage at these two loci. Methods. Clinical data and DNA samples were collected from affected family members. Polymorphic microsatellite markers spanning the critical regions on chromosome 1 and chromosome 16 that encompass MCKD1 and MCKD2 were analyzed. Two-point and multipoint LOD scores were calculated. Results. The family fulfilled previously published criteria for the diagnosis of MCKD, but hyperuricemia and gout were not prominent features. Twenty-one affected individuals were identified. Mean age at death or end-stage renal disease was 47 years (37 to 60). Linkage and haplotype analysis generated strongly negative results at MCKD1 on chromosome lq21 (two-point LOD score = -5.32). Strong evidence of linkage to MCKD2 was generated with a maximum multi-point LOD score of 3.75. Conclusion. These results provide the first independent confirmation of a gene predisposing to MCKD on chromosome 16p12 and indicate that mutation of this gene is not restricted to a single family or population. The absence of hyperuricemia and gout in our family indicates that these are not obligatory features of MCKD2 mutations.