A 20-year-old woman was admitted to the hospital for further evaluation of her renal function.At age 17, she was diagnosed with hypertension (systolic blood pressure, 150 mmHg), and at age 19, her systolic blood pressure was 180 mmHg and she had hyperuricemia (uric acid, 12.7 mg/dL) and decreased renal function (serum creatinine, 3.39 mg/dL).Urinalysis showed no proteinuria or abnormal urinary sediment, but a computed tomography scan revealed renal atrophy, a right kidney cyst, and small calcifications in both kidneys.Kidney biopsy tissue showed severe tubulointerstitial fibrosis in approximately 90% of the cortical region.Scattered portions of the proximal tubules remained undamaged.Most distal tubules were damaged, and Von Kossa staining showed that they contained scattered small calcifications.The patient's father had a history of dialysis, so genetic testing was performed.A heterozygous missense variant c.247T> C (p.Cys83Gly) was found in exon 3. A UMOD gene variant was considered because severe interstitial fibrosis as seen in this case is specific to autosomal dominant tubulointerstitial kidney disease-UMOD; the decline in renal function was presumed to be due to distal tubular damage caused by impaired uromodulin secretion and subsequent fibrosis.Hyperuricemia, which is rare in young women, is known to be a complication of this disease, but its significance is not fully understood.We speculated that in the present case, hyperuricemia, combined with hypertension and the numerous, scattered areas of nephrocalcinosis, may have been another factor in the progression of renal failure.
Hane et al. (Fri,) studied this question.