B73-24 Necrotizing Cavitary Pneumonia Secondary to Invasive Group a Streptococcus in a Young Immunocompetent Adult

Abstract Introduction Invasive Group A streptococcal (iGAS) infections are uncommon but carry high morbidity and mortality, with an estimated incidence of 3.5-8.2 per 100,000 people yearly. Pneumonia accounts for approximately 11% of iGAS cases. Following the COVID-19 pandemic, there has been an increase in iGAS infections among immunocompetent individuals, often following viral upper respiratory infections. Clinical and radiographic presentations can mimic pulmonary tuberculosis, invasive fungal lung diseases, or non-infectious granulomatous conditions, creating significant diagnostic challenges. Case Presentation A 33-year-old male who works as an emergency room physician presented with a 10-day history of low-grade fever, malaise, myalgia, non-productive cough, and dyspnea. He had been taking ibuprofen prior to presentation. On examination he was in acute respiratory distress requiring supplemental oxygen. He had right lung crackles. Initial chest radiograph showed a right upper lobe and supra-hilar opacity. Blood and throat cultures both grew Streptococcus pyogenes. Chest CT scan revealed a thick-walled cavitary lesion in the right upper lobe measuring 5.2 × 4.2 × 4.3 cm, with surrounding ground-glass opacities. Despite initial treatment with Ceftriaxone and Azithromycin, his fever, leukocytosis, and acute hypoxic respiratory failure worsened. Quantiferon and Acid-fast bacilli (AFB) were negative. Repeat imaging demonstrated progressive cavitary necrotizing pneumonia with bilateral opacities, parapneumonic effusions, and right hilar adenopathy. The hospital course was complicated by sub-massive hemoptysis. Following multidisciplinary consultation, antibiotics were escalated sequentially to penicillin G and clindamycin, then linezolid and meropenem after bronchoscopy and bronchoalveolar lavage revealed no additional pathogens. The patient gradually improved and was discharged on a six-week course of oral linezolid, showing marked clinical and radiologic recovery. Discussion Invasive GAS pneumonia primarily affects young children and older adults, especially those with chronic illnesses or social vulnerabilities. However, invasive infection can arise in healthy adults especially in the context of viral co-infection or the presence of invasive species such as strains M1 and M3. NSAIDs use has been hypothesized to worsen disease progression by impairing neutrophil function, augmenting pro-inflammatory cytokine production and masking early symptoms. This could be a contributing factor for the fulminant course of iGAS necrotizing pneumonia in this immunocompetent young adult. This case emphasizes the need for early presentation to the hospital, recognition, aggressive antimicrobial escalation, and multidisciplinary collaboration. Conclusion Necrotizing pneumonia due to iGAS is an uncommon but life-threatening condition in healthy adults. Prompt diagnosis, early aggressive therapy, and coordinated team management are vital to improve survival and prevent long-term complications. This abstract is funded by: None