B71-25 A Diagnostic Crossroad: Infectious or Immune-mediated Granuloma

Abstract Introduction Granulomas represent an organized aggregation of macrophages in response to persistent inflammatory stimuli, ranging from infectious agents (e.g., non-tuberculous mycobacteria NTM, fungi, tuberculosis) to autoimmune processes (e.g., vasculitis, sarcoidosis) or foreign materials. The overlapping clinical, serologic, and radiographic features can obscure the distinction between infection-related and immune-mediated granulomatous diseases. This report highlights the complexity inherent in discerning between these etiologies, showcasing a unique diagnostic dilemma encountered in clinical practice. Case Description A 24-year-old female with a history of microscopic polyangiitis (p-ANCA, MPO positive), asthma, chronic pain syndrome, and ADHD presented with prolonged dry cough and mild hemoptysis over nine months. She was afebrile, presenting leukocytosis (17.7k) and procalcitonin 0.14. Computed tomography of the chest revealed multiple bilateral cavitary and nodular lesions. The patient lacked travel exposure, sick contacts, and substance use history. Serological workup demonstrated a markedly elevated myeloperoxidase titer (1:640) but no evidence of HIV, coccidioidomycosis, or aspergillus IgE. Sputum cultures on two occasions identified Mycobacterium abscessus. Robotic bronchoscopy with cryobiopsy and bilateral BAL yielded necrotizing granulomas with positive AFB stains and an eosinophilic infiltrate; cultures confirmed M. abscessus and Aspergillus species.Therapeutic management commenced with corticosteroids targeting presumed vasculitis; antifungal therapy (voriconazole) was initially started but subsequently discontinued due to suspected colonization. Prolonged immunosuppressive therapy (avacopan and rituximab) failed to yield clinical improvement, while radiologic assessment demonstrated resolution of cavitation and reduction of nodular lesions in the absence of antimycobacterial therapy. Given persistent symptoms despite these radiographic improvements, an E-consultation was submitted to the National Jewish Health Infectious Disease Program in Denver. At the time of this abstract, the outcome of the expert consultation remains pending. Discussion This case exemplifies the substantial overlap in clinical and radiological manifestations of NTM pulmonary disease and ANCA-associated vasculitis. The coexistence of severe asthma, immunosuppressive treatment, and autoimmune vasculitis creates significant diagnostic and therapeutic ambiguity, as both contribute to increased susceptibility and mimicry of NTM-related disease1. Although the patient fulfilled established criteria for NTM-PD, spontaneous radiographic resolution absent antimycobacterial therapy raises the possibility of immune-mediated resolution. The ongoing multidisciplinary evaluation—including specialized infectious disease input—underscores the necessity of precision in diagnosis and management to avoid both under-treatment of infection and excess immunosuppression, especially in complex granulomatous pulmonary disease. This abstract is funded by: None