A 55-year-old man was admitted to our institution for the assessment of abnormal chest shadows. He had non-alcoholic fatty liver disease and visited the gastroenterologist regularly. He complained of dry cough, dyspnea on exertion, and anorexia for the preceding 2 months. A chest radiograph revealed bilateral central consolidation (Fig. 1A).
On admission, his vital signs were as follows: blood pressure, 115/96 mmHg; pulse rate, 94 beats/min; respiratory rate, 18 breaths/min; SpO2, 93% in room air; and body temperature, 36.4  C. Auscultation revealed fine crackles in the right upper chest at the end of inspiration. Blood examination results revealed that the lymphocyte and serum immunoglobulins were nearly normal, and the anti-HIV antigen/antibody test was negative. Serum Krebs von den Lungen-6 (KL-6) and (1-3)-beta-D-glucan levels were elevated (4007 U/mL and 217.1 pg/mL, respectively) (Table 1).
Chest computed tomography (CT) revealed bilateral central consolidation with peripheral sparing, some accompanied by cysts and traction bronchiectasis (Fig. 1B and C). Bronchoscopy performed under mild sedation using midazolam and pethidine without intubation revealed normal endobronchial airways. The bronchial alveolar lavage fluid comprised histiocytes, 96%; neutrophils, 1%; and lymphocytes, 3%; the polymerase chain reaction for P. jirovecii was positive. Pathologically, a transbronchial lung biopsy (TBLB) specimen of the right upper and lower lobes showed granulomatous inflammation highly infiltrated with inflammatory cells, mainly macrophages, obscuring the alveolar structure. Furthermore, in the alveolar spaces, accumulation of periodic acid-Schiff-positive foamy eosinophilic materials was observed, while Grocott methenamine silver (GMS) stain revealed cystic forms of P. jirovecii (Fig. 2A-C).
The peripheral blood CD4+ lymphocyte count was 508/muL. No signs of neoplastic disease were detected during full-body contrast-enhanced CT, 18Fluorodeoxyglucose-positron emission tomography/CT, upper gastrointestinal endoscopy, and bone marrow puncture. In addition, the patient had no history of recurrent infections or family history of immunodeficiency. Thus, there was no suspicion of primary immunodeficiency or secondary immunodeficiency such as malignancy, HIV infection, or drug-induced immunodeficiency. Therefore, the patient was diagnosed as an immunocompetent patient with PCP. Trimethoprim (960 mg/day) and sulfamethoxazole (4800 mg/day) were administered for 3 weeks without steroids. The patient's symptoms and chest radiograph findings improved with treatment (Fig. 3). His serum KL-6 and (1-3)-beta-D-glucan levels, which were elevated at diagnosis, continued to decrease to normal ranges after treatment; no recurrence occurred during the 18 months following the discontinuation of trimethoprim and sulfamethoxazole.