A pedigree research on mutation sites of the uromodulin-encoding gene from a patient with familial juvenile hyperuricemic nephropathy

Objective To draw enough attention from nephrologists to familial juvenile hyperuricemic nephropathy (FJHN), this paper reported a case with FJHN presented by a novel mutation of uromodulin (UMOD) gene from the proband, his oldest son, and his nephew, together with literature review. Methods Clinical manifestations and laboratory data of the proband were collected and analyzed. Mutations of exon 2-5 of UMOD-encoding gene of proband, his eldest son, and nephew were measured. Meanwhile, clinical relevant data of other members of the family were collected, validated, and analyzed. Results The proband presented with typical clinical features of FJHN, including juvenile onset, obvious hyperuricemia, gout arthritis, gout stone, early increased nocturia and other manifestations indicating decrease of urinary concentration function, continuous and slow progression of renal function damage, and occurrence of end-stage renal disease at the age of about 40 years. Pedigree investigation showed that at least 12 members within three generations of the family suffered from hyperuricemia, 3 of whom died of uremia, and the proband was also suffering from uremia and receiving hemodialysis. Gene measuring showed that the proband and his eldest son had the same genetic mutation: a novel sense heterozygous chimerical mutation at the 4th exon of UMOD-coding gene was identified in the proband and his eldest son, so that, in the amino acid sequence, the 285th alanine (A, GCG) changed to glutamic acid (E, GAG), which was a newly discovered gene mutation. His nephew without hyperuricemia had no mutation on exon 2-5. Conclusion FJHN is an autosomal dominant disorder. If an adolescent has symptoms of remarkable hyperuricemia, gout, and a family history of chronic kidney disease, FJHN should be considered, and need to be recognized through medical imaging, renal biopsy, and UMOD gene mutation test, so that early correct diagnosis of FJHN should be made and misdiagnosis be avoided. Key words: Familial juvenile hyperuricemic nephropathy; Hyperuricemia; Uromodulin; Gene mutation; End-stage renal disease