A 28-year-old patient with acute lymphoblastic leukemia and neutropeni
a developed necrotizing enterocolitis and Clostridium septicum bactere
mia, followed by rhabdomyolysis, skin rash, and acute neurologic chang
es. Numerous cortical leptomeningeal enhancements were present on head
MRI. Meningeal and brain biopsy showed segmental, full-thickness lysi
s of smooth muscle cells of medium-sized meningeal vessels with overal
l preservation of the structure of the vessel wall.