Paroxysmal nocturnal hemoglobinuria presenting with acute kidney injury in an 18-year-old male: a case report.

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired hematological disease resulting from somatic PIGA gene mutations. These mutations cause a deficiency in glycosylphosphatidylinositol-anchored-anchored proteins such as CD55 and CD59 on blood cell surfaces, leading to uncontrolled complement-mediated hemolysis. Although this condition is typically identified in individuals in their third or fourth decades of life, diagnosis during late adolescence is rare. Renal complications are a known feature of PNH; however, they present more frequently as a gradual decline in function rather than as a severe acute insult. This report describes the unusual case of an 18-year-old male who presented with a 6-month history of intermittent dark urine followed by an acute illness. Laboratory evaluation revealed severe Coombsnegative hemolytic anemia, significantly elevated lactate dehydrogenase levels, and acute kidney injury requiring immediate hemodialysis. Renal biopsy-confirmed pigment nephropathy, and high-sensitivity flow cytometry detected a large PNH clone, establishing the diagnosis of classical PNH. The patient's renal function improved with supportive care, but hemolysis persisted. This case highlights the fact that PNH can manifest in young adults with acute kidney injury as the primary presenting symptom. Including PNH in the differential diagnosis of patients with unexplained hemolytic anemia and renal impairment is crucial, even in atypical age groups. Prompt diagnosis is vital for initiating appropriate management, including supportive measures and the consideration of complementary inhibitor therapy, to improve outcomes.