Hemophagocytic lymphohistiocytosis secondary to Pneumocystis jirovecii pneumonia: a rare case report.

Hemophagocytic lymphohistiocytosis (HLH) secondary to Pneumocystis jirovecii pneumonia (PJP) is extremely rare in children. We present the case of a 10-year-old girl with a history of idiopathic thrombocytopenic purpura (ITP) on long-term oral prednisone, who was admitted for progressive fever, cough, and dyspnea. Metagenomic next-generation sequencing of blood and bronchoalveolar lavage fluid confirmed PJP. Despite targeted antifungal therapy and respiratory support, she developed persistent high-grade fever, pancytopenia, hyperferritinemia, hypofibrinogenemia, and hemophagocytosis on bone marrow aspirate by day 10, meeting diagnostic criteria for HLH. Genetic testing was declined by the parents. Management included dexamethasone, continuous renal replacement therapy, and plasmapheresis. Unfortunately, her condition deteriorated, and she was discharged upon parental request on day 22, succumbing on the same day. To our knowledge, this is the first reported pediatric case of HLH secondary to PJP in China. This case highlights that in children with PJP-especially those on immunosuppressive therapy-the development of persistent fever and cytopenia should prompt immediate evaluation for secondary HLH to enable timely intervention.