Primary granulomatous angiitis of the CNS preferentially involving small veins with a granulomatous leukoencephalitis‐like lesion in the cerebrum

We have reported an autopsy case of primary granulomatous angiitis of the CNS preferentially involving the small veins with a granulomatous leukoencepalitis‐like lesion in the cerebral white matter of a 48‐year‐old man. The latter lesion was ischemic necrosis due to circumferential multiple perivenous granulomas in the adjacent V irchow‐ R obin space. Multifocal progressive involvement of venular adventitia by granulomas, leaving behind mural fibrosis and luminal stenosis, was related clinically to the prolonged stepwise deterioration observed in the patient, and pathologically to diffuse loosening with dilated veins in the deep cerebral white matter and subcortical hemorrhagic infarction in the left parietal lobe through chronic venous stagnation. PCR demonstrated negativity for M ycobacterium tuberculosis and P ropionibacterium acnes , and in situ hybridization with EBV ‐encoded small nuclear RNA probe was also negative. The possibility of subarachnoidal latent infection with an unknown avirulent agent causing exclusively perivascular granulomas is proposed. It will be necessary to examine by autopsy whether the type (artery or vein) and size of the involved vessels and the pathological subtype of angiitis is related to the etiopathogenesis and prognosis. It is also pointed out that the entity of lymphocytic angiitis is problematic.