A3-04 Pulmonary Presentation of Systemic Inflammation: Autoinflammatory Disease Masquerading as Malignancy

Abstract

Autoinflammatory syndromes are increasingly recognized as heterogeneous disorders of innate immune dysregulation, often overlapping in clinical and genetic features. Although pulmonary manifestations are uncommon, several autoinflammatory conditions such as VEXAS syndrome, juvenile rheumatoid arthritis, adult-onset Still’s disease, and Familial Mediterranean Fever can produce inflammatory pulmonary nodules that mimic metastatic malignancy. Recognition of these presentations is critical, as they can respond dramatically to immunosuppressive therapy once the correct diagnosis is established. We describe a diagnostically challenging case of a young adult male initially suspected to have metastatic lung cancer, whose evaluation ultimately suggested a previously uncharacterized autoinflammatory process. We present a 26-year-old previously healthy male with progressive dry cough, exertional dyspnea, diffuse myalgias, small joint arthritis involving the fingers, wrists, and ankles, tendonitis, a Gottron-like rash on the hands and lower extremities, low-grade fevers, and occasional bloody stools. Initial external workup revealed a right infrahilar mass, right lower lobe pleural thickening, small pleural effusion, and mediastinal and hilar lymphadenopathy on CT chest, with corresponding PET activity. Initially suspected to have metastatic lung cancer, he was informed his prognosis was poor. However, transbronchial, EBUS, and mediastinal lymph node biopsies showed only active inflammation without malignancy. On presentation to our facility, a broad differential was pursued, with suspicion for an autoinflammatory or autoimmune etiology. Pulmonary function testing was normal. Laboratory evaluation revealed ESR >100, elevated CRP, positive ANA (1:160), negative HLA-B27, normal ferritin, and negative S100 staining. Cytokine analysis showed elevated TNF, IL-6, MCP-1, IL-2, and IL-18. Targeted variant testing identified a UBA1 gene variant, c.123G>T p.(M41L), with low-level mosaicism (0.004%), and a heterozygous MEFV mutation. Although his ethnicity made Familial Mediterranean Fever unlikely, these findings raised the possibility of overlapping somatic and germline contributions to innate immune activation. He was treated empirically with immunosuppression for a presumed multisystem inflammatory disorder, resulting in resolution of symptoms and marked radiologic improvement. This case highlights the expanding spectrum of adult-onset autoinflammatory diseases that may present with pulmonary findings mimicking malignancy. The coexistence of low-level UBA1 mosaicism and MEFV mutation suggests a potential interaction between somatic and inherited variants in triggering inflammation. Similar to the recent discovery of VEXAS syndrome, this case may represent a novel subtype of autoinflammatory disease. Continued genomic and immunologic investigation is warranted, as timely recognition and immunosuppressive therapy can lead to dramatic recovery.

This abstract is funded by: None