Influenza and Pneumocystis jirovecii pneumonia in an allogeneic hematopoietic stem cell transplantation recipient: Coinfection or superinfection?

Influenza infection and Pneumocystis jirovecii pneumonia (PJP) in hematopoietic stem cell transplant (HSCT) patients are well characterized; however, no dual infections have been reported in this patient population and little evidence of mechanisms of interaction between the two infections exists. We present a 53-year-old male allogeneic HSCT patient on immunosuppressive therapy for the treatment of graft versus host disease initially diagnosed with influenza A H3 and later PJP. Despite the development of acute respiratory distress syndrome, the patient was successfully treated with appropriate antimicrobial therapy and aggressive supportive care. This case demonstrates the necessity of maintaining a high index of suspicion for fungal (including PJP) coinfection or superinfection in the setting of worsening influenza infection.