Background: Cocaine/Levamisole-Associated Autoimmune Syndrome (CLAAS) encompasses a spectrum of autoimmune and vasculitic phenomena, which includes Cocaine-Induced Midline Destructive Lesions (CIMDL), which can mimic ANCA-associated vasculitis (AAV) due to overlapping clinical features and the potential for ANCA positivity. These similarities can lead to misdiagnosis and inappropriate immunosuppressive therapy. Methods: This study highlights a case series of seven patients (from 2015 to 2024) with CLAAS with its subset of CIMDL, initially misdiagnosed as active AAV, in patients who were referred to various clinicians in the Rheumatology unit of a Tertiary Hospital in the United Kingdom. Results: All patients presented with nasal symptoms, and they all exhibited additional systemic manifestations consistent with CLAAS. Five were ANCA-positive at initial evaluation, leading to the initiation of immunosuppressive therapy; however, symptoms persisted. The diagnoses were then revised to CIMDL in all cases within the broader context of CLAAS following the identification of cocaine use after further patient enquiry and urine toxicology for drug of abuse (DOA) screening found cocaine metabolites. Conclusion: A comprehensive drug history and urine toxicology screening are crucial in patients with suspected AAV, as ANCA positivity can occur in CLAAS as well as its subset of CIMDL, complicating the diagnosis. Differentiating between AAV and CIMDL related to CLAAS is essential to avoid unnecessary immunosuppression.

IntroductionAutoimmune inner ear disease (AIED) is a condition first described by McCabe in 1979 based on a diagnostic study on a cohort of patients[1] who presented with bilateral sensorineural hearing loss (SNHL) with a specific clinical pattern that did not fit with existing diagnoses and demonstrated audiometric improvement with corticosteroid and immunosuppressive therapy. The pathogenesis of AIED is not completely understood, though several mechanisms have been proposed, including uncontrolled humoral and cell-mediated reactions against inner ear antigens, [2] resulting in autoantibody development and T-cell responses. [3]AIED accounts for <1% of SNHL cases [2]but may be under-diagnosed due to a lack of standardised diagnostic criteria. [4] The main treatment has been corticosteroids; however, the overall reported response is 60-70%[2] and only 14% remain responsive after 34 months. [5] There is a risk of further decline in hearing in the absence of therapy. Alternative immunosuppressive treatments [3] were tried but these have yielded variable results. There is no standard treatment protocol for AIED following corticosteroids as randomised controlled trials are limited.[6] Here, we report a case of AIED in a patient that responded well to infliximab.