Sanfilippo A and Sanfilippo B syndromes, also known as mucopolysaccharidosis III or MPS IIIA or MPS IIIB, are lysosomal storage diseases (LSD) that arise from a deficiency in the gene encoding for the enzyme N-sulphoglucosamine sulphohydrolase (SGSH), or N-acetyl alpha-glucosaminidase (NAGLU), respectively, which result in a buildup of complex sugars within the brain.
Sanfilippo A and B syndromes cause 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 and B are considered the most common forms of LSD, with an incidence of 1 in 70,000 live births worldwide.1
1 Genetics of Mucopolysaccharidosis Type III. Medscape. WebMD LLC, 1994-2014 http://emedicine.medscape.com/article/948540-overview