Pulmonary Co-infection with Cryptococcus Species and Pneumocystis jirovecii in an Old Patient Without a Previous Predisposing Illness

Background Cryptococcosis and pneumocystosis are opportunistic infections which are more common in immunosuppressed individuals. Herein, we report a rare case of coinfection of pulmonary cryptococcosis (PC) and Pneumocystis jirovecii pneumonia (PJP) in a patient without a previous predisposing illness. Case presentation A 76-year-old man was admitted to our hospital with complaints of cough, expectoration, shortness of breath, and fever. A chest computed tomography (CT) showed multiple nodules with diffuse ground-glass opacities (GGOs) in both lungs. The patient was diagnosed as extrinsic allergic alveolitis (Pigeon breeder’s lung). After treatment with corticosteroids, the patient improved with significant absorption of GGOs on chest CT. However, pulmonary nodules gradually enlarged and such lesions could not be explained by EAA. Based on the positivity of serum cryptococcal antigen and pathological examination of lung nodule which confirmed the presence of Cryptococcus spores, PC was diagnosed later and fluconazole was administered. However, repeated chest CT performed about 2 months after antifungal treatment showed significantly increased GGOs in both lungs. The pathological examination of new lung lesions revealed the presence of P. jirovecii. The patient was finally diagnosed having coinfection of PC and PJP and sulfamethoxazole was further prescribed. Thereafter, the patient improved again with significant absorption of GGOs as noted on chest CT. Conclusions Concomitant PC and PJP is very rare, especially in a patient without a previous predisposing illness. Additionally, when pulmonary lesions cannot be completely explained by one kind of infectious disease, the possibility of mixed infection should be considered.