Sanfilippo A syndrome, also known as mucopolysaccharidosis III or MPS III, is a lysosomal storage disease that arises from a deficiency in the gene encoding for the enzyme N-sulphoglucosamine sulphohydrolase (SGSH), which results in a buildup of complex sugars.

Sanfilippo A syndrome causes progressive intellectual disability and the loss of previously acquired skills (developmental regression). Unlike many other forms of MPS, symptoms often appear after the first year of life. A decline in learning ability typically occurs between ages 2 and 6. The child may have normal growth during the first few years, but final height is below average. Delayed development is followed by deteriorating mental status.

In later stages of the disorder, people may experience seizures and movement disorders.

Sanfilippo A is considered the most common form of LSD, with an incidence of 1 in 70,000 live births worldwide. 1


Reference:

1 Genetics of Mucopolysaccharidosis Type III. Medscape. WebMD LLC, 1994-2014 http://emedicine.medscape.com/article/948540-overview