At present, MPS III is terminal.
At this time, only palliative care is available.
Life expectancy varies based on Sanfilippo type and individual progression, but is typically around 15 years.
Sanfilippo has its most devastating effects on the brain.Children experience hyperactivity, sleeplessness, loss of speech, loss of toileting skills, intellectual disability, heart problems, vision loss, seizures, loss of mobility, dementia, and finally death.

The disease progression can vary significantly from one child to the next, making it particularly difficult to predict.
Symptoms cover a wide spectrum and some children may experience particular symptoms more than others.