Microscopic polyarteritis presenting with chest infections and acute appendicitis.

We describe a 38-year-old male with antineutrophil cytoplasmic auto-antibody (ANCA) positive microscopic polyarteritis who presented with recurrent chest infections, lung haemorrhage, renal insufficiency and acute appendicitis. Appendectomy was followed by resolution of abdominal symptoms and the surgical specimen revealed vasculitis of the serosal vessels. A renal biopsy was performed because of impaired renal function and this revealed focal necrotising glomerulonephritis with absence of immune deposits. Chest infections were treated with antibiotics resulting in partial clinical response, but pulmonary symptoms relapsed and a complete resolution was achieved only after plasma exchange and the administration of cyclophosphamide. Our observation emphasises the protean manifestations of microscopic polyarteritis and the relationship between ANCA and disease activity.