Pneumocystis jirovecii pneumonia as an initial manifestation of hyper-IgM syndrome in an infant: A case report

Kim, Danbi; Shin, Ju Ae; Han, Seung Beom; Chung, Nack-Gyun; Jeong, Dae Chul

His vital signs were as follows: heart rate, 134 beats/min; respiratory rate, 49 breaths/min; and body temperature, 37.1°C. Physical examination revealed no accessory breathing sounds on chest auscultation and chest wall retractions despite tachypnea. Chest X-ray showed bilateral diffuse haziness without definite cardiomegaly (Fig. 1A) . Echocardiography revealed an ejection fraction of 78.7% without any anatomical and functional abnormalities. Blood tests revealed a white blood cell count of 22,250/mm 3 , hemoglobin levels of 16.5 g/dL, platelet count of 536,000/mm 3 , and C-reactive protein levels <0.02 mg/dL without any abnormal findings in blood chemistry. We suspected interstitial lung disease of non-infectious causes or afebrile viral pneumonitis, and a multiplex polymerase chain reaction (PCR) test for respiratory viruses was performed using a nasopharyngeal swab. Although there were no family and individual histories consistent with PID, a PCR test for Pneumocystis jirovecii was also performed using a nasal swab, considering interstitial pneumonitis accompanying severe hypoxemia without accessory breathing sounds. After admission, his respiratory rate increased to 60 to 90 breaths/min, and mechanical ventilator care was initiated on hospital day (HD) #2. Empirical intravenous trimethoprim/sulfamethoxazole (TMP/SMX; 5 mg/kg of TMP thrice a day) treatment for possible PCP was also initiated on HD #2. Methylprednisolone (2 mg/kg twice a day) was also administered for possible interstitial pneumonitis of noninfectious causes. Chest computed tomography showed diffuse homogeneous opacity occupying alveolar spaces throughout the whole lung fields (Fig. 2) . The multiplex PCR test for respiratory viruses revealed negative results for influenza virus, parainfluenza virus, respiratory syncytial virus, adenovirus, human metapneumovirus, rhinovirus, coronavirus, and human bocavirus. Bronchoscopy was performed on HD #3; however, any findings of definite airway inflammation and increased pulmonary secretion were not observed. The results of the PCR test for P. jirovecii performed on admission were reported as positive on the evening of HD #3. After then, negative culture results for bacteria, cytomegalovirus, and Mycobacterium tuberculosis were reported in bronchial washing fluid samples; cysts of P. jirovecii were observed on Gomori methenamine silver stains of bronchial washing fluids. Weaning of ventilator care and tapering of methylprednisolone doses were initiated on HDs #6 and #8, respectively. Chest X-ray findings showed improvement 2 weeks since initiating treatment (Fig. 1) , and he was extubated on HD #23. Oxygen supply and methylprednisolone treatment were completed on HDs #28 and #29, respectively. A repeat PCR test for P. jirovecii showed a positive result 3 weeks after initiating TMP/SMX treatment. The PCR test showed a negative result 4 weeks after initiating treatment, and the TMP/SMX treatment was converted to prophylaxis (150 mg/m 2 /day of TMP, thrice a week on alternate days) on HD #29. He was discharged from the hospital on continuing TMP/SMX prophylaxis on HD #34.