(880) A Rare Cause of Severe Pediatric Acute Respiratory Distress Syndrome

Introduction: CD40 ligand Deficiency (CD40LD) is a rare X-linked immunodeficiency which causes defects in T cell proliferation and immunoglobulin isotype class switch. Patients with CD40LD are at risk of sinopulmonary and gastrointestinal opportunistic infections, autoimmune disorders, and neoplasms. We report a case with an initial presentation of severe pediatric acute respiratory distress syndrome (PARDS) due to pneumocystis jirovecii pneumonia (PJP).

Description: Patient was a 6-month-old previously healthy male who presented with rhinovirus and adenovirus (ADV) bronchiolitis. Within 24 hours of admission, he acutely worsened to severe PARDS with an oxygenation index (OI) of 23.4 and required high ventilator settings (PIP 35, PEEP 14, FiO2 100%, iNO 20 ppm). His unusually rapid progression led to a wide infectious, immunologic, and genetic investigation. CT chest showed diffuse ground-glass opacities and interlobular septal thickening with ‘crazy paving’ appearance. Work-up revealed PJP and disseminated ADV found on bronchoalveolar lavage (BAL) and blood culture, respectively. He had undetectable IgG and IgA, and flow cytometry was diagnostic for CD40LD. He was subsequently treated with trimethoprim/sulfamethoxazole, methylprednisolone, and intravenous immunoglobulin with rapid improvement. He was extubated on hospital day (HD) 5 and transferred out of the ICU on HD 9.

Discussion: Acute isolated hypoxemia with rapidly progressing ARDS should raise suspicion for PJP and underlying immunodeficiency. CD40LD is rare and requires a prompt multidisciplinary approach for a timely diagnosis. Management includes supportive care, treating opportunistic infections, and eventual hematopoietic stem cell transplant.