貧血を伴う小児における高尿酸血症およびクレアチニン上昇

Anemia in infancy is a frequent clinical challenge, often attributed to nutritional deficiencies. However, persistent or unexplained anemia warrants further investigation. In this case report, we describe an infant in whom anemia was first identified at six months of age; however, the underlying etiology became apparent only after the development of elevated serum creatinine and hyperuricemia.

We present a 1.7-year-old boy with persistent normocytic anemia, hyperuricemia, and elevated creatinine, initially evaluated for hematologic causes without a clear diagnosis. Despite normal growth, laboratory findings revealed hypouricosuria, hyposthenuria, and mildly decreased kidney function. Imaging and immunologic work-up were unremarkable. Due to multisystem involvement, genetic testing was performed and identified a heterozygous variant in REN gene, suggesting a potential link to autosomal dominant tubulointerstitial kidney disease (ADTKD). Due to persistent anemia refractory to iron therapy, erythropoietin was initiated at a dose of 0.50 µg/kg/week, resulting in a 1.9 g/dL increase in hemoglobin after one month. The family was appropriately informed about the chronic nature of the kidney disease, and a lifelong follow-up strategy was established.

This case underscores the importance of considering ADTKD in pediatric patients presenting with unexplained anemia and mild kidney impairment, even in the absence of a family history. Early diagnosis can prevent unnecessary procedures such as kidney biopsy, allow the timely initiation of supportive treatments, and improve long-term outcomes. Pediatricians, pediatric hematologists and pediatric nephrologists should be aware of this diagnostic possibility, particularly when anemia is accompanied by hyperuricemia and elevated creatinine in infancy.