Severe, delayed-onset thrombocytopenia after prolonged chlorothiazide use in a former preterm infant with bronchopulmonary dysplasia: a case report

Abstract Introduction Drug-induced immune thrombocytopenia (DITP) is a rare, antibody-mediated adverse effect that typically occurs within days to weeks of drug exposure and is rarely reported in infants receiving prolonged diuretic therapy. Case presentation We report a former 28-week preterm infant with bronchopulmonary dysplasia who developed severe isolated thrombocytopenia (7 × 10⁹/L) after more than three months of chlorothiazide therapy. The infant presented with petechiae and mucosal bleeding at 5 months chronological age (2 months corrected age). Extensive evaluation excluded infectious, malignant, and consumptive causes. Bone marrow examination showed no evidence of leukemia or aplasia, with findings compatible with peripheral platelet destruction, and monoclonal antibody immobilization of platelet antigens (MAIPA) confirmed chlorothiazide-dependent anti-GPIIb/IIIa antibodies. Chlorothiazide was discontinued and IVIG administered, resulting in rapid platelet recovery to normal within one week. Long-term follow-up at 6 months corrected age demonstrated sustained normal platelet counts, appropriate growth (7.8 kg, 30th percentile), and normal neurodevelopment by ASQ screening, with no further bleeding or infectious complications. Conclusion This case highlights a rare delayed-onset presentation of chlorothiazide-induced immune thrombocytopenia in infancy. It underscores the importance of considering medication-related causes in isolated thrombocytopenia and supports routine hematologic monitoring during prolonged thiazide therapy.