Canavan disease: A progressive, inherited disorder of the central nervous system that is caused by a deficiency of the enzyme aspartoacylase. Signs appearing in children between 3 and 6 months of age include developmental delay, significant motor slowness, enlargement of the head (macrocephaly), loss of muscle tone (hypotonia), poor head control, and severe feeding problems. As the disease progresses, seizures, shrinkage of the nerve to the eye (optic atrophy), and often blindness develop, as do heartburn (gastrointestinal reflux) and deterioration of the ability to swallow. Canavan disease is inherited as an autosomal recessive condition, with both parents silently carrying a single Canavan gene and each of their children running a 25 percent risk of receiving both genes and having the disease. Canavan disease is more prevalent among individuals of Eastern European Jewish (Ashkenazi) background than in others. There is currently no effective treatment and affected children die in the first decade of life. Also known as spongy degeneration of the central nervous system and Canavan-Van Bogaert-Bertrand disease.