Myocardial infarction and leg amputation due to critical limb ischaemia as an initial manifestation of granulomatosis with polyangiitis

Granulomatosis with polyangiitis (GPA) is a rare autoimmune vasculitis primarily affecting the respiratory tract and kidneys. This case report describes a severe and atypical presentation of GPA in a 42-year-old male, who initially presented with sudden onset of cough, myalgia, dysaesthesia, and lower limb oedema. Initial tests indicated elevated inflammatory markers and white blood cell count. Subsequent imaging revealed a suspicious pulmonary nodule, but the patient experienced a syncopal episode and myocardial infarction before scheduled surgery. Despite normal myocardial biopsy results and negative bacterial/viral tests, the patient developed ischaemic symptoms in the lower extremities, leading to severe limb ischaemia and amputation of the left distal third thigh. Few days later he developed renal involvement with proteinuria, haematuria, active urinary sediment, and rapidly progressive renal dysfunction. The clinical scenario and the detection of high-titre antineutrophil cytoplasmatic antibodies (ANCA) were highly suggestive for GPA; despite the lack of histological confirmation due to mandatory anticoagulant treatment for the recent myocardial event, treatment with methylprednisolone and rituximab was started and led to rapid clinical improvement. Subsequently histological analysis of the amputated leg confirmed necrotising vasculitis. This case highlights the importance of considering GPA in differential diagnoses involving multiorgan symptoms and underscores the complexities in diagnosing and managing this rare condition, especially when typical diagnostic biopsies are not feasible.