Respiratory-Predominant Relapsing Polychondritis: The Role of Pet Scan in Making this Challenging Diagnosis.

Relapsing polychondritis is a rare, immune-mediated, multisystemic disease characterized by recurrent inflammation of cartilaginous and proteoglycan-rich tissues. Its diagnosis may be challenging due to its rarity and wide clinical variability. It can be primary or associated with other autoimmune conditions. Recently, it has been associated with an autoinflammatory disease known as vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome. We present a case of a 65-year-old man with respiratory-predominant relapsing polychondritis. This case illustrates the diagnostic complexity of relapsing polychondritis, where multiple initial investigations were inconclusive. We highlight the pivotal role of the fluorine-18 fluorodeoxyglucose positron emission tomography scan, which provided the key evidence of cartilaginous inflammation, ultimately guiding the diagnosis in this atypical presentation. LEARNING POINTS: Atypical presentations of relapsing polychondritis may present with isolated respiratory symptoms and constitutional signs in the absence of auricular or nasal chondritis.In older male patients with relapsing polychondritis features and myelodysplastic syndromes, vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome must be considered, requiring detection of somatic ubiquitin-like modifier-activating enzyme 1 gene mutations.When histopathology is unavailable, positron emission tomography imaging and clinical criteria are key to diagnosis.