Autosomal Dominant Tubulointerstitial Kidney Disease—UMOD: Case Report and Disease Update

Background and Clinical Significance: Autosomal dominant tubulointerstitial kidney disease caused by a mutation in the uromodulin gene (ADTKD-UMOD) is a rare kidney disorder characterized by progressive tubulointerstitial damage and a slowly progressive loss of renal function. ADTKD is often under-recognized in the clinical setting. Diagnosis of ADTKD-UMOD can be challenging due to its nonspecific symptoms and is confirmed by genetic testing alone. Case presentation: We report the case of a 42-year-old male patient referred for evaluation of renal dysfunction, which was accidentally discovered during routine laboratory checks. He had no significant medical history and no known family history of kidney disease or gout. Physical examination was unremarkable. Renal dysfunction was confirmed, with serum creatinine at 1.44 mg/dL and eGFR at 59.5 mL/min/1.73 m2. Urinalysis was within physiological limits, proteinuria being 75 mg/day. Uric acid was mildly elevated (7.5 mg/dL) without a history of gout. Other laboratory findings, including autoantibodies, were in the normal range. The patient underwent a kidney biopsy, though it was not diagnostic, showing mild focal tubular atrophy and interstitial fibrosis without glomerular involvement. Immunofluorescence staining was negative for complement and immunoglobulins. Given the above nonspecific findings, the patient was suspected of having possible ADTKD. Genetic investigation using a clinical exome next-generation sequencing approach identified a novel heterozygous missense variant in the UMOD gene (c.409T>C; p.Cysteine137Arginine (p.Cys137Arg)) that is likely pathogenic. The patient is under regular clinical-laboratory monitoring. After one year, his overall health is good, renal function is stable with no proteinuria, and uric acid is mildly increased without gout attacks. Conclusions: Increased clinical awareness is crucial for detecting ADTKD-UMOD. Genetic testing can help to resolve clinical diagnostic challenges in patients with unexplained decreased kidney function.