MPS III

Mucopolysaccharidosis III-Sanfilippo syndrome

Sanfilippo syndrome is an autosomal recessive disorder with four recognized subtypes based on the four different enzymes of heparan sulphate metabolism (types A-D). When the enzymes needed to break down the heparan sulfate sugar chain are missing or are defective, storage develops and symptoms result. The four recognized subtypes of MPS III are:

1. Sanfilippo type A is the most severe form from a deficiency of an enzyme called heparan N-sulfatase located on chromosome 17q25.3.
2. Sanfilippo type B is due to a deficiency of alpha-N-acetylglucosaminidase located on chromosome 17q21.
3. Sanfilippo C is from a deficiency of Heparan-alpha-glucosaminide N-acetyltransferase located on chromosome 8p11-q13.
4. Sanfilippo D is from a deficiency of N-acetylglucosamine 6-sulfatase located on chromosome 12q14.

Sanfilippo syndrome is possibly the most common form of MPS. It is seen in about 1 in 70,000 births. Often symptoms may not become apparent until 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 first few years, but final height is below average. Delayed development can be followed by deteriorating mental status. Other symptoms include:

1. Walking problems
2. Coarse facial features
3. Full lips
4. Heavy eyebrows that meet in the middle of the face above the nose
5. Diarrhea
6. Stiff joints that may not extend fully
7. Aggressive and hyperkinetic behavior