Sulfadiazine-Induced Crystalline Nephropathy: A Reversible Cause of Acute Kidney Injury in Advanced HIV

Introduction: Crystal-induced acute kidney injury (AKI) is caused by the intratubular precipitation of crystals, which results in obstruction. Crystal-induced AKI mostly occurs as a result of acute uric acid nephropathy and following the administration of drugs or toxins that are poorly soluble. Case Description: A 23-year-old man with history of untreated HIV presented with 1 week history of right sided weakness. HIV viral load was 274,000 copies/mL and absolute CD4 count was 2 /cu mm. Brain MRI showed bilateral ring enhancing lesions. Patient was empirically started on pyrimethamine 75 mg daily, sulfadiazine 1.5 g every 6 hours and leucovorin 25 mg daily. Brain biopsy confirmed the diagnosis of toxoplasmosis. Hospital course was complicated by AKI 8 days after the initiation of this regimen. Labs revealed BUN 12 mg/dL and serum creatinine 2.0 mg/dL (baseline 0.8 mg/dL). Urinalysis showed no hematuria or pyuria with urine pH of 6. Urine protein/creatinine ratio was 0.42 g/g. Kidney ultrasound showed non-obstructing bilateral ureteral stones. Examination of urine sediment under polarized light revealed multiple yellow brown asymmetric rosette shaped crystals (sulfonamide crystals) (Fig. 1). Sulfadiazine was discontinued and patient was switched to clindamycin. Patient was treated with IV fluids (sodium bicarbonate) to alkaline the urine (urine pH goal was > 7 with urine output goal was 2 L/day). The patient’s serum creatinine returned to baseline within 8 days. Discussion Sulfadiazine induced crystalluria is a serious complication in patients with AIDS who are treated for toxoplasmosis. Predisposing factors include high dose of sulfadiazine and volume depletion. It usually presents with AKI within 3 weeks of starting the medication. Treatment requires stopping the offending agent, aggressive IV hydration (urine output at least 1.5 L/day) and bicarbonate infusion to alkaline the urine (goal pH > 7). Conclusion This case highlights sulfadiazine-induced crystal nephropathy as a reversible cause of AKI. Early drug withdrawal, aggressive hydration, and urinary alkalinization are crucial for recovery. Preventive measures, especially hydration and urine pH monitoring, can significantly reduce risk.