Canavan disease

Canavan disease is a rare and fatal autosomal recessive degenerative disease that causes progressive damage to nerve cells and loss of white matter in the brain, resulting from a deficiency of the enzyme aspartoacylase that leads to breakdown of the myelin insulating nerve fibers. Because it is autosomal recessive, a child has a 25 percent chance of being affected when both parents carry the defective gene. The severe form typically appears in early infancy, between three and six months old, with intellectual disability, loss of motor skills, feeding difficulties, abnormal muscle tone, poor head control and an enlarged head; advanced cases may involve paralysis, blindness or seizures, and this form typically causes death or life-threatening complications by age ten. A milder, later-onset variant exists with minimal developmental delay and little effect on lifespan. The disease predominantly affects people of Eastern European Jewish ancestry, among whom about one in 40 carries the gene.