Atypical familial juvenile hyperuricemic nephropathy associated with a hepatocyte nuclear factor-1β gene mutation

Abstract

Background. Familial juvenile hyperuricemic nephropathy (FJHN) is a dominantly inherited condition characterized by young-onset hyperuricemia, gout, and renal disease. The etiologic genes are unknown, although a locus on chromosome 16 has been identified in some kindreds. Mutations in the gene encoding hepatocyte nuclear factor (HNF)-1β have been associated with dominant inheritance of a variety of disorders of renal development, particularly renal cystic disease and early onset diabetes; hyperuricemia has been reported in some kindreds. Methods. To assess a possible role for the HNF-1β gene in some FJHN kindreds we sequenced the HNF-1β gene in subjects from three unrelated FJHN families with atypical features of renal cysts or abnormalities of renal development. We also compared serum urate levels in subjects with HNF-1β mutations with populations of controls, type 2 diabetic subjects, and subjects with mild chronic renal failure without HNF-1β mutations. Results. A splice-site mutation in intron 2, designated IVS2+IG>T, showed complete co-segregation with FJHN in one family with diabetes. Serum urate levels were significantly higher in the HNF-1β subjects compared with the normal control subjects (384 μmol/L vs. 264 μmol/L, P = 0.002) and the type 2 diabetic subjects (397 μmol/L vs. 271 p, mol/L, P = 0.01). Comparison of serum urate levels in the HNF-1β subjects with gender-matched subjects with renal impairment of other causes did not reach significance (402 μmol/L vs. 352 μmol/L, P = 0.2). Conclusion. Hyperuricemia and young-onset gout are consistent features of the phenotype associated with HNF-1β mutations, but the mechanism is uncertain. Families with HNF-1β mutations may fit diagnostic criteria for FJHN. Identification of HNF-1β patients by recognizing the features of diabetes and disorders of renal development is important in resolving the genetic heterogeneity in FJHN.