An atypical presentation of microscopic polyangiitis without renal involvement in an older patient with falls, bilateral lower limb swelling and neuropathy

Microscopic polyangiitis (MPA) is a primary systemic small-vessel vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA). The condition is uncommon among the UK population, although it increases with age. MPA manifests heterogeneously and may affect any organ, although glomerulonephritis is almost always present. This case report describes a rare presentation of MPA with isolated mononeuritis multiplex, without glomerulonephritis or other hallmark features, and reflects the varied manifestations of MPA and challenges in recognising the condition. Awareness of MPA is essential to timely diagnosis, treatment initiation and improved health outcomes. MPA-related neuropathy damages nerve vasculature, typically causing mononeuritis multiplex, and may predispose older adults to falls. Treatment involves managing the underlying vasculitis through immunosuppression; however, treatment complications arising from immunosuppression are common in older adults, increase with frailty and may complicate management. Therefore, a multidisciplinary approach is necessary, and an understanding of the condition from geriatric perspectives is key.