When Pneumocystis Jirovecii Strikes: A ‘Pneumo'-numental Challenge Revealing New HIV Diagnosis in a Child

Abstract Introduction: There is a broad differential for respiratory failure in infants, and it's difficult to prioritize workup in a child with acute life-threatening decompensation. We describe a case where a stepwise approach revealed a new HIV diagnosis. Case: A 7-month-old full term boy developed 2 days of cough, congestion, and fever. He was admitted to outside hospital for hypoxemic respiratory failure requiring 6L HFNC with presumed bronchiolitis.He was growing well (weight-for-length 75th%ile) with no past respiratory infections. His chest x-rays showed diffuse hazy opacities. On hospital day 7, his chest CT showed homogenous ground glass opacities (GGOs), concerning for interstitial lung disease (ILD) (Figure1A/B). He transferred to our PICU for expedited ILD workup with biopsy. Rapidly worsening hypoxemia unresponsive to non-invasive respiratory support led to emergent escalation onto VV ECMO. Initial work-up with bronchoalveolar lavage (BAL) showed diffuse alveolar hemorrhage (DAH). BAL fluid was positive for Pneumocystis jirovecii on direct fluorescent antibody stain (Figure1C). Biopsy was deferred. Immunodeficiency workup was initiated, with high suspicion for primary immunodeficiency unmasked by waning maternal antibodies. However, he was found to have reactive HIV antigen/antibody testing with viral load 6.63 million copies/mL, and CD4% 4%. He started high dose trimethoprim/sulfamethoxazole, steroids, and antiretroviral therapy (ART). He decannulated from ECMO 3 days later and extubated to HFNC 1 day after. Follow-up chest CT 3 months later showed resolution of diffuse GGOs with residual bilateral reticular pulmonary opacities, reflective of atelectasis and scarring (Figure1D). His mother had regular prenatal care with negative HIV testing in the first trimester. She was recently notified by the health department about possible HIV exposure but hadn't pursued workup. The child had presumed vertical transmission. Discussion: As HIV rates in infants have decreased in the US with prenatal testing and early treatment with ART, a diagnosis of PJP in early childhood is rare. We present a case of acute respiratory failure due to PJP as the initial manifestation of undiagnosed HIV. Post-mortem autopsies suggest DAH might be more commonly associated with PJP than previously thought. It's important to maintain a high suspicion for rare infectious etiologies of unexplained acute respiratory failure. PJP diagnosis should generate further testing for primary or secondary immunodeficiencies. HIV has been associated with long-term reduction in lung function in children with vertical transmission, due to both primary HIV and opportunistic infections. Pediatric pulmonologists play an important role in evaluating both acute and chronic sequalae of HIV infection.