Vasculitides (Polyarteritis Nodosa / GPA) - Orthopaedic Relevance

Because this combination - a foot drop, which could be a mononeuritis multiplex, together with digital ischaemia and constitutional symptoms of fever and weight loss and raised inflammatory markers - points to a systemic vasculitis rather than an isolated entrapment neuropathy or simple peripheral vascular disease. The vasculitides are inflammatory disorders of blood vessels classified by vessel size: large-vessel disease such as giant-cell and Takayasu arteritis, medium-vessel disease such as polyarteritis nodosa, which causes mononeuritis multiplex, digital and limb ischaemia and skin lesions and tends to spare the lungs and be ANCA-negative, and small-vessel ANCA-associated disease such as granulomatosis with polyangiitis. Musculoskeletally these cause arthralgia, myalgia and a usually non-erosive arthritis, but the dangerous manifestations are exactly what this patient has - vasculitic neuropathy causing a foot or wrist drop, and limb and digital ischaemia that can progress to gangrene. The key point is that if I treat only the limb - decompress the nerve or amputate gangrenous tissue - without recognising and treating the vasculitis, the disease will continue and the tissue loss will progress. So I would recognise the systemic picture, confirm with ANCA and other serology, biopsy or angiography, and start urgent immunosuppression with corticosteroids and either cyclophosphamide or rituximab, treating any trigger such as hepatitis B in polyarteritis nodosa, and I would perform any necessary surgery alongside, not instead of, controlling the underlying disease.