Renal tubular acidosis (RTA) is a normal anion gap metabolic acidosis that manifests with insufficiency of hydrogen ion excretion or bicarbonate (HCO₃) reuptake as a result of renal tubular dysfunction independent of glomerular filtration rate. Hypokalemic RTA subtypes co-existing with autoimmune diseases particularly appear in Sjogren’s syndrome, but rarely in systemic lupus erythematosus (SLE). Type 4 RTA associated with hyperkalemia is very rare during the course of SLE and hence has been scarcely reported in the literature. Here, we report a 42-year-old patient for whom regular follow-up was ongoing due to class IV lupus nephritis when she developed hyperkalemia. The patient had normal anion gap hyperkalemic metabolic acidosis and her urine pH was 5.5. Type 4 RTA was considered and, therefore, tests for renin and aldosterone levels were requested, which revealed that renin was suppressed and aldosterone was decreased. Upon diagnosis of SLE-associated type 4 RTA, short-term oral HCO₃ and fludrocortisone were initiated. Potassium (K) and HCO₃ levels improved at day 15 of therapy. In this review, we analyzed our case along with five other reports (a total of seven cases) of SLE-associated type 4 RTA we identified through a literature search. We wanted to highlight RTA for differential diagnosis of hyperkalemia emerging during SLE/lupus nephritis and we also discussed possible underlying mechanisms.

肾小管酸中毒 (RTA) 是一种正常的阴离子间隙代谢性酸中毒，表现为氢离子排泄或碳酸氢盐 (HCO ₃) 肾小管功能障碍导致的再摄取，与肾小球滤过率无关。与自身免疫性疾病共存的低钾 RTA 亚型特别出现在干燥综合征中，但很少出现在系统性红斑狼疮 (SLE) 中。与高钾血症相关的 4 型 RTA 在 SLE 病程中非常罕见，因此在文献中几乎没有报道。在这里，我们报告了一名 42 岁的患者，她在出现高钾血症时因 IV 级狼疮性肾炎而定期随访。患者有正常阴离子间隙高钾代谢性酸中毒，尿液 pH 值为 5.5。考虑了 4 型 RTA，因此要求检测肾素和醛固酮水平，结果表明肾素受到抑制，醛固酮减少。诊断为 SLE 相关 4 型 RTA 后，短期口服 HCO₃和氟氢可的松开始使用。钾 (K) 和 HCO ₃水平在治疗第 15 天有所改善。在本综述中，我们分析了我们的病例以及我们通过文献检索确定的其他五份 SLE 相关 4 型 RTA 报告（共七份病例）。我们想强调 RTA 用于鉴别诊断 SLE/狼疮性肾炎期间出现的高钾血症，我们还讨论了可能的潜在机制。