Case Presentation: A 60-year-old man with a history of alcohol use disorder was admitted to the emergency department due to difficulty moving. The patient was cachectic, agitated, febrile, and tachycardiac. Laboratory results showed hemoglobin 3.2 g/dL, MCV 150.4 fL, WBC 3,300/µL (83% neutrophils, 6.5% lymphocytes), platelets 178,000/µL, LDH 403 U/L, BUN 79.9 mg/dL, creatinine 2.72 mg/dL, vitamin B1 1.2 µg/dL, vitamin B12 181 pg/mL, and folic acid 1.1 ng/mL. The patient was diagnosed with vitamin deficiency, megaloblastic anemia, Wernicke’s encephalopathy, alcohol withdrawal syndrome, dehydration, and acute kidney injury. Treatment included blood transfusion, vitamins B1 and B12 supplementation, and benzodiazepines. On day 6, the patient developed hypoxemia, and CT scan revealed bilateral pneumonia. Piperacillin/tazobactam was initiated; however, his respiratory status worsened. Given a β-D-glucan of 114 pg/mL, pneumocystis pneumonia (PCP) was suspected, and HIV antibodies were negative. The patient declined intubation, and bronchoscopy was not performed because of severe respiratory failure. Trimethoprim/sulfamethoxazole (TMP-SMX) and prednisolone were initiated, resulting improvement in the respiratory status. Renal function also improved, prompting an adjustment in the TMP-SMX dose based on kidney function, with a planned 21-day course of treatment. However, on day 14 of TMP-SMX treatment, the patient developed hypoglycemia, which progressively worsened, reaching 20 mg/dL by day 17. Blood insulin levels were abnormally high, but CT findings did not suggest an insulinoma. TMP-SMX-induced hypoglycemia was suspected and the drug was discontinued. Glucose levels stabilized the following day, and insulin concentrations normalized. Nutritional management was continued, and after rehabilitation, the patient was discharged home independently.
Discussion: PCP is an opportunistic infection caused by Pneumocystis jirovecii and is commonly observed in HIV/AIDS patients or in immunocompromised patients due to chemotherapy or immunosuppressive drugs. Several reports have documented PCP in malnourished non-HIV patients, suggesting that malnutrition alone may predispose individuals to PCP(1-3). Sputum tests for Pneumocystis jirovecii have low sensitivity. When bronchoscopy cannot be performed, treatment should be initiated based on clinical findings, imaging, and laboratory data. The first-line treatment for PCP is TMP-SMX, which inhibits microbial folate synthesis. Although TMP-SMX alone rarely causes hypoglycemia, the risk increases when used with other hypoglycemic agents or in the presence of renal dysfunction or malnutrition(4,5). In this case, the dose of TMP-SMX was adjusted according to renal function, but the underlying malnutrition related to chronic alcohol dependence likely contributed to the hypoglycemic episodes.
Conclusions: Malnourished non-HIV patients are at increased risk of developing pneumocystis pneumonia. TMP-SMX can cause severe hypoglycemia, particularly in patients with renal dysfunction or nutritional deficiencies.