Pneumocystis carinii pneumonitis in haemophagocytic lymphohistiocytosis

We report on a 10-y-old boy who developed Pneumocystis carinii pneumonitis (PCP) as the dominant symptom at the onset of haemophagocytic lymphohistiocytosis (HLH). PCP is a common infection in patients with combined primary immunodeficiencies or acquired immunodeficiency syndrome but it has rarely been observed at the onset of HLH. Typically, HLH presents as a febrile syndrome associated with cytopenia and hepatosplenomegaly. Repeated bone marrow aspirates, spleen or lymph node biopsies are sometimes required to reveal haemophagocytosis. Because of the significant immunosuppression during treatment of HLH, prophylaxis of PCP with co-trimoxazole is recommended. However, de-arranged immune response in HLH renders the patients susceptible to opportunistic infections, even before the introduction of immunosuppressants. Conclusion: We suggest that in patients with unclear respiratory symptoms, it is worth considering a differential diagnosis of HLH.