Renal salt-wasting syndrome with tubular copper deposition in a heterozygous ATP7B carrier: a case report

BACKGROUND: ATP7B mutations classically lead to Wilson’s disease, characterized by hepatic and neurological involvement due to systemic copper overload. However, renal-limited phenotypes are extremely rare, easily overlooked and clinically diverse. Here, we report a woman carrying a heterozygous ATP7B variant who presented with isolated salt-wasting syndrome, marked renal copper deposition. CASE PRESENTATION: We report a 30-year-old Chinese woman with renal salt-wasting syndrome and chronic kidney disease, without hepatic, neurological, or ophthalmologic abnormalities. Laboratory tests, including ceruloplasmin (0.20 g/L), 24-h urinary copper (20.8 µg/24 h), and liver function were within normal or borderline ranges, not fulfilling Wilson’s disease diagnostic criteria (Leipzig score < 4). Renal biopsy revealed marked copper accumulation within tubular epithelial cells, and immunohistochemistry showed reduced ATP7B expression. Whole-exome sequencing identified a heterozygous ATP7B mutation (c.2621 C > T, p.Ala874Val). Given the absence of systemic copper overload, the patient was treated with corticosteroids and electrolyte replacement rather than copper-chelating agents, leading to partial clinical improvement. CONCLUSION: This case suggests a possible renal-limited phenotype in an ATP7B carrier, underscoring the importance of integrating genetic testing and histopathology in unexplained tubulointerstitial nephritis. Long-term follow-up is essential to monitor for potential systemic manifestations.