The infant, who had been receiving chlorothiazide for the respiratory complications characteristic of bronchopulmonary dysplasia, presented at five months of chronological age, equivalent to two months of corrected age, with petechiae and mucosal bleeding. When bloodwork came back, the platelet count had plummeted to 7 × 10⁹ per liter, a level so low that spontaneous bleeding becomes a serious clinical concern. Normal platelet counts generally range well above 150 × 10⁹ per liter, meaning this infant had lost more than 95 percent of circulating platelets despite having tolerated the drug for over a quarter of a year.

What makes this case medically remarkable is its timing. Drug-induced immune thrombocytopenia, or DITP, is an antibody-mediated adverse effect that typically announces itself within days to weeks of drug exposure. The immune system, in susceptible individuals, generates antibodies that recognize a drug bound to platelet surfaces, marking the platelets for destruction by the spleen. In this infant, however, the reaction emerged only after more than three months of continuous therapy, a delayed onset that could easily have misled clinicians toward other diagnoses and delayed the correct intervention.

The diagnostic workup was exhaustive. Because isolated thrombocytopenia in an infant carries a long differential diagnosis, the clinical team systematically excluded infectious causes, including congenital and acquired viral infections, as well as malignant and consumptive processes such as disseminated intravascular coagulation. Neonatal alloimmune thrombocytopenia, in which maternal antibodies cross the placenta and attack fetal platelets, was also considered and ruled out. A bone marrow examination showed no evidence of leukemia or aplastic failure; instead, the findings were compatible with peripheral platelet destruction, the hallmark of an immune-mediated process occurring in the bloodstream rather than a failure of platelet production in the marrow.

The definitive answer came from a specialized laboratory technique known as monoclonal antibody immobilization of platelet antigens, or MAIPA. This assay can detect antibodies that bind to platelet glycoproteins only in the presence of a specific drug. In this case, the testing confirmed chlorothiazide-dependent antibodies directed against glycoprotein IIb/IIIa, the integrin receptor that platelets use to aggregate and form clots. The demonstration of drug-dependent anti-GPIIb/IIIa antibodies transformed the case from a diagnostic puzzle into a clear example of chlorothiazide-induced immune thrombocytopenia, an entity almost never reported in infants receiving prolonged diuretic therapy.

Treatment followed the established logic of immune-mediated platelet destruction. The offending drug was discontinued immediately, and intravenous immunoglobulin, or IVIG, was administered. IVIG works through several mechanisms, including saturating the Fc receptors on macrophages in the spleen so that antibody-coated platelets escape destruction. The response was rapid and decisive: the infant’s platelet count returned to normal within one week, confirming that removing the drug and damping the immune destruction was sufficient to reverse the condition without further intervention.

Long-term follow-up added reassuring context to an alarming episode. At six months of corrected age, the child maintained sustained normal platelet counts, showed appropriate growth at 7.8 kilograms, placing the infant at the 30th percentile, and demonstrated normal neurodevelopment on Ages and Stages Questionnaire screening. No further bleeding or infectious complications were documented. The complete recovery underscores that, once the trigger is identified and removed, drug-induced immune thrombocytopenia in infancy can resolve fully without lasting consequences.

The clinical lesson embedded in this case is one of vigilance rather than alarm. Chlorothiazide remains a cornerstone of therapy for infants with bronchopulmonary dysplasia, where it helps reduce pulmonary edema and improve respiratory mechanics, and serious adverse reactions remain exceedingly rare. But the authors argue that the rarity of the reaction is precisely why it can be overlooked. When a preterm infant on prolonged thiazide therapy presents with isolated thrombocytopenia, medication-related causes deserve a place near the top of the differential, even when the drug has been tolerated for months without incident.

The case also highlights the value of modern immunological diagnostics in pediatrics. Without MAIPA testing, the connection between chlorothiazide and the platelet destruction would have remained presumptive, resting on temporal association and the exclusion of alternatives. By confirming drug-dependent antibodies against a specific platelet glycoprotein, the clinicians converted suspicion into proof, a distinction that matters both for the individual patient, who can now avoid the drug permanently, and for the broader medical record, where confirmed cases inform future prescribing decisions and pharmacovigilance databases.

For the community of neonatologists and pediatric hematologists who care for the growing population of surviving extremely preterm infants, the report supports a simple but consequential practice change: routine hematologic monitoring during prolonged thiazide therapy. The infant at the center of this case survived a platelet count that, unrecognized, could have led to catastrophic hemorrhage. That the outcome was instead a full recovery with normal development reflects both the resilience of the child and the diagnostic persistence of the clinical team, and it offers a cautionary, ultimately hopeful, data point for a rare reaction hiding inside a very common prescription.

Subject of Research: Chlorothiazide-induced immune thrombocytopenia in a former preterm infant with bronchopulmonary dysplasia

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

Article References: Adi, M., Ishmuradov, B., Husanov, S., Kuziev, O., & Ashraf, A. (2026). Severe, delayed-onset thrombocytopenia after prolonged chlorothiazide use in a former preterm infant with bronchopulmonary dysplasia: a case report. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07742-1

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07742-1

Keywords: drug-induced immune thrombocytopenia, chlorothiazide, bronchopulmonary dysplasia, preterm infant, thrombocytopenia, diuretics, MAIPA, platelet antibodies, adverse drug reaction, neonatology, IVIG, pediatrics