P18 Bullous leukocytoclastic vasculitis in a patient with known undifferentiated autoimmune rheumatic disease

Abstract Introduction A 55-year-old woman with undifferentiated autoimmune rheumatic disease (uAIRD) and chronic leg ulcers presented with a progressive bullous eruption on her legs. During her admission, she developed visual disturbance, hearing loss, and brain lesions were discovered on imaging. There was diagnostic uncertainty between an infective process versus an inflammatory vasculitis as the driver for her presentation. Despite an infection work-up, including multiple blood cultures and an ASOT test, no infection was identified. Ultimately, a skin biopsy showed leukocytoclastic bullous vasculitis. This case demonstrated a complex presentation of cutaneous vasculitis, where differentiation from infection was difficult, as is often the case. Case description A 55-year-old woman presented to the emergency department, after being referred by her general practitioner, with a high CRP and a new bilateral blistering rash on her lower limbs. She had a history of recurrent leg ulcers, juvenile idiopathic arthritis (JIA), and uAIRD, with skin rash and peripheral neuropathy, and was receiving treatment with azathioprine, hydroxychloroquine and abatacept. Previous skin biopsies of the leg ulcers had shown post-inflammatory changes and non-specific ulceration. On examination, she exhibited lower limb oedema and erythema with localised blisters. Blood tests at time of presentation showed a mild acute kidney injury (AKI), and elevated CRP (186mg/L), white cell count (WCC)(34x109/L) and neutrophils (31x109/L). The patient was ANA positive, anti-Ro and anti-RNP positive, ANCA positive, but MPO and PR3 negative, dsDNA negative, and C3 was low whilst C4 was normal. Given the initial impression of an infectious process, antibiotics were initiated, and a skin biopsy was performed. The following morning the patient developed sudden-onset unilateral vision loss and auditory change. MRI head and orbits revealed multiple parenchymal brain lesions suggestive of either inflammatory or embolic aetiology, with no orbital abnormalities. The ophthalmology team suspected bilateral central retinal vein occlusion. The patient awaits formal audiometry. Swabs of the skin lesions grew Staphylococcus aureus, Proteus mirabilis, and Corynebacteria. MRI ankle suggested deep soft tissue infection without osteomyelitis. A PET-CT did not highlight any medium/large vessel vasculitis, malignancies or abscesses. Treatment with antibiotics did not result in any clinical improvement, or impact on