OBSOLETE: Familial juvenile hyperuricemic nephropathy type 1

Familial juvenile hyperuricemic nephropathy type 1 (FJHN1) is an obsolete disease entry that has been reclassified. This condition was previously described as an autosomal dominant disorder characterized by early-onset hyperuricemia (elevated uric acid levels in the blood), gout, and progressive kidney disease leading to chronic renal failure. The disease primarily affects the renal (kidney) system and joints. Patients typically present in adolescence or young adulthood with decreased uric acid excretion by the kidneys, resulting in elevated serum uric acid, gouty arthritis, and a gradual decline in kidney function that can progress to end-stage renal disease. This entry (Orphanet code 209886) is now obsolete because the condition has been reclassified under the broader category of autosomal dominant tubulointerstitial kidney disease caused by mutations in the UMOD gene (ADTKD-UMOD). The UMOD gene encodes uromodulin (Tamm-Horsfall protein), which is the most abundant protein in normal urine and is produced by cells of the thick ascending limb of the loop of Henle in the kidney. Mutations in UMOD lead to abnormal protein folding, endoplasmic reticulum stress, and progressive tubulointerstitial fibrosis. Management of this condition includes the use of allopurinol or febuxostat to lower uric acid levels, which may help control gout symptoms and potentially slow renal disease progression, although evidence for renal protection is limited. Ultimately, patients with progressive kidney failure may require renal replacement therapy, including dialysis or kidney transplantation. Patients and families should be referred to the updated disease classification (autosomal dominant tubulointerstitial kidney disease due to UMOD mutations) for the most current clinical guidance.

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