The February COM: A man of 78 years with idiopathic late-onset cerebellar ataxia developed renal failure in association with a high ESR and positive pANCA. This was complicated by a subclinical spinal subarachnoid hemorrhage which was related to necrotizing inflammation of small leptomeningeal vessels. Renal cortical infarcts were due to similar inflammation in arcuate and interlobular arteries. Spinal subarachnoid hemorrhage is rare and usually due to rupture of an arteriovenous malformation. However, an immunogenic connective tissue disorder should be considered in the differential diagnosis. In this case, the histology and results of an autoantibody screen support a diagnosis of microscopic polyangiitis.