B63-06 Pneumomediastinum and Pulmonary Interstitial Emphysema as a Presenting Symptom of Pneumocystis Jiroveci Infection in X-linked Agammaglobulinemia

Abstract Introduction X-linked agammaglobulinemia (XLA) is a rare primary humoral immunodeficiency characterized by severe hypogammaglobulinemia and recurrent bacterial infections. We present an atypical presentation of XLA: an infant presenting with pneumomediastinum and pulmonary interstitial emphysema (PIE) found to have Pneumocystis jiroveci (PJP) infection. Case Presentation A 3-month-old term male infant presented with new onset respiratory distress. CT chest revealed a large pneumomediastinum; the patient was admitted on high-flow nasal cannula support due to pneumomediastinum in the setting of presumed bronchiolitis, although viral symptoms were absent and viral testing was negative. Given this unusual presentation, Whole Exome Sequencing (WES) was sent on day 4 of admission. Respiratory support was weaned to low-flow nasal cannula, but the patient did not tolerate discontinuation of support despite two courses of systemic steroids. Further workup with sweat chloride was completed (negative). Repeat chest CT revealed significant PIE through multiple lobes with resolved pneumomediastinum. A bronchoscopy was attempted, however due to desaturations with anesthesia the procedure was aborted prior to scope insertion. One week following attempted procedure, acute decompensation secondary to tension pneumothorax prompted PICU transfer, intubation, and chest tube placement. WES returned positive for XLA pathogenic variant. Given identified immunodeficiency, PJP testing (endotracheal culture) was collected and resulted positive. After initiation of trimethoprim-sulfamethoxazole and intravenous immunoglobulin, the patient had rapid improvement and was extubated. The patient was discharged with outpatient Pulmonology and Immunology follow-up. Discussion This case represents an unusual presentation of XLA: pneumomediastinum/PIE as a consequence of PJP infection. This was a diagnostically challenging case, especially as the patient was unable to undergo bronchoscopy due to intolerance of anesthesia (desaturations). PJP is an opportunistic infection most frequently associated with HIV and abnormal T-cell function; typical presentation is cough, fever, and pneumonia. On literature review, there have been 3 cases identified of PJP as the presenting infection in XLA. All presented with typical pneumonia symptoms, not with pneumomediastinum/PIE. There have been infrequent reports of pneumomediastinum/PIE as the presenting symptom of PJP, though this is a rare presentation in infants. This case increases awareness of PJP infection as a presenting symptom of XLA, and pneumomediastinum/PIE as a consequence of PJP. While PJP is classically associated with compromised T-cell function, it is an opportunistic organism capable of infection in patients with agammaglobulinemia. This case highlights the importance of evaluation for immunodeficiency and rapid genetic testing in severe, atypical pulmonary presentations in infancy. This abstract is funded by: None