Paroxysmal nocturnal hemoglobinuria with a positive Coombs test presenting as acute kidney injury: a case report.

This report presents the case of a 60-year-old woman who was admitted with symptoms of fatigue and poor appetite. Laboratory investigations revealed severe acute kidney injury (AKI), indicated by a serum creatinine level of 2,065 μmol/L, necessitating the initiation of emergency hemodialysis. The patient also exhibited hemolytic anemia (hemoglobin, 69 g/L), thrombocytopenia (platelet nadir, 45 × 109/L), venous thrombosis, a positive direct antiglobulin test (DAT), and a low absolute reticulocyte count. Conventional flow cytometry (red blood cells and neutrophils CD55/CD59) did not detect a paroxysmal nocturnal hemoglobinuria (PNH) clone. Renal biopsy revealed hemoglobin cast nephropathy and intrarenal venous thrombosis. Subsequent bone marrow evaluation, high-sensitivity flow cytometry (FLAER method), and supportive PIGA sequencing findings established the diagnosis of PNH. Treatment with eculizumab led to hematologic remission and progressive renal recovery. This case underscores the importance of considering PNH in patients with severe AKI and hemolysis, even when initial conventional flow cytometry is negative.