Mucopolysaccharidosis type IIIA (MPS IIIA), or Sanfilippo syndrome type A, is a rare inherited neurodegenerative disorder. Children with MPS IIIA do not produce enough enzyme activity to break down a substance in the body called heparan sulfate.
As heparan sulfate accumulates, it affects the normal functions of the body and, in particular, the brain. The lack of enzyme activity is due to a defective gene that would normally instruct the cells of the body to make a functional enzyme. The defective gene is called N-sulfoglucosamine sulfohydrolase (SGSH).
Signs and symptoms usually become apparent in early childhood and include speech problems, development delays, challenging behaviors, extreme hyperactivity and poor sleep.
MPS IIIA has a worldwide incidence of up to 1.62 per 100,000 live births.