Unsuspected Pneumocystis carinii pneumonia at presentation of severe primary immunodeficiency

BACKGROUND Pneumocystis carinii is an important pathogen in immunodeficiency but may be an unrecognised cause of respiratory compromise. OBJECTIVES To ascertain the incidence of P carinii pneumonia (PCP) at presentation of severe combined immunodeficiency (SCID), whether it had been diagnosed, and the effect of treatment on outcome. SETTING The supraregional paediatric bone marrow transplant unit for primary immunodeficiencies at Newcastle General Hospital. METHODS Retrospective case note review of infants referred with a diagnosis of SCID from 1992 to 1998. RESULTS Ten of 50 infants had PCP at presentation; only one was diagnosed before transfer. Eight were diagnosed by bronchoalveolar lavage and two by lung biopsy. In only one was P carinii identified in nasopharyngeal secretions. Five required ventilation for respiratory failure but all were successfully treated with co-trimoxazole and methylprednisolone with or without nebulised budesonide. Nine survived to bone marrow transplantation and four are long term survivors after bone marrow transplantation; no deaths were related to PCP. CONCLUSIONS PCP is a common presenting feature of SCID but is rarely recognised. Bronchoalveolar lavage or lung biopsy are needed for diagnosis. Treatment with co-trimoxazole is highly successful.