Abstract
A 67-year-old man was admitted to our hospital complaining of dry cough. Chest computed tomography showed diffuse infiltrates and ground-glass opacities in the bilateral lung fields. Transbronchial lung biopsy specimens showed alveoli filled with yeast-like fungi. With a diagnosis of pneumocystis pneumonia (PCP), he was given oral sulfamethoxazole/trimethoprim, to which he responded well. However, seven months later, PCP relapsed. Analyses revealed a low bronchoalveolar lavage fluid CD4/CD8 ratio of 0.04 and CD4+ lymphocytopenia (250/μL). Despite intensive work-up, we were unable to detect the underlying cause of CD4+ lymphocytopenia; therefore, a final diagnosis of idiopathic CD4+ T-lymphocytopenia was made.