Thrombotic thrombocytopenic purpura in a child with Alexander's disease.

Thrombocytopenic purpura developed in a 14-year-old boy with Alexander's disease; he died. The proximity of Rosenthal fibers to small vessels in the brain, the presence of perivascular lymphocytes in the brain, and the presence of complement in renal arterioles suggest that the Rosenthal fibers could have injured the endothelium-basement membrane resulting in an immune response triggering the thrombotic thrombocytopenic purpura.