CADASIL, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; CARASIL, cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy; CARASAL, cathepsin a-related arteriopathy with strokes and leukoencephalopathy; MELAS, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; HIV, human immunodeficiency virus; EBV, Epstein–Barr virus; CMV, cytomegalovirus. The gene discussed is CTSS; the disease is lactic acidosis.