Lysomal Storage Disorder

The Dwarf Pony

Mucopolysaccharidosis Type III

The subtypes of mucopolysaccharidosis III (MPS III) A,B,C and D are caused by lysosomal enzymes that are responsible for the degradation of heparan sulfate, an essential component of nerve cell membranes. This explains why in this mucopolysaccharidosis predominantly the central nervous system is affected and the patients have only slight dysmorphic features. First symptoms such as agitated behaviour and learning difficulties, mainly regarding speech development, appear at the age of  3-5 years. Later on epileptic seizures occur, at the end the patients get tetraspastic, most die at the age of around 20 years. The subtypes A.B,C and D do not show any difference in clinical phenotype.

Mucopolysaccharidosis Type III | SphinCS - Clinical Science for LSD

Synonym: Sanfilippo syndrome

Mucopolysaccharidosis Type IIIA. Deficient enzyme: Heparan-sulfamidase
Mucopolysaccharidosis Type IIIB. Deficient enzyme: N-acetyl-alpha-glucosaminidase
Mucopolysaccharidosis Type IIIC. Deficient enzyme: N-acetyltransferase
Mucopolysaccharidosis Type IIID. Deficient enzyme: N-acetyl-glucosamin-6-sulfate-sulfatase

Mucopolysaccharidosis Type IIIA. Gene: SGSH
Mucopolysaccharidosis Type IIIB. Gene: NAGLU
Mucopolysaccharidosis Type IIIC. Gene: HGSNAT
Mucopolysaccharidosis Type IIID. Gene: GNS

Mode of inheritance: Autosomal recessive


  • Severe form
  • Attenuated form

Leading symptoms:
Severe form
(Age of onset:  )

  • Psychomotor development delay/ regression
  • Behavioral disorder
  • Hyperaktivity
  • Sleep disorder
  • Epilepsy
  • Joint contractures

Attenuated form
(Age of onset: childhood/ adolescence)

  • Loss of cognitive and motor skills
  • Psychiatric symptoms


  • Measurement of the activity of heparan-sulfamidase (Type IIIA), N-acetyl-alpha-glucosaminidase (Type IIIB), N-acetyltransferase (Type IIIC), N-acetyl-glucosamin-6-sulfat-sulfatase (Type IIID) in leukocytes or serum or plasma
  • Molecular genetic analysis of the appropriate gene: SGSH, NAGLU, HGSNAT, GNS

Only symptomatic

Current Studies

The "U.S. National Library of Medicine" provides a complete list of all international studies at The comparable EU website is less comprehensive:

Self-help groups

Gesellschaft für Mukopolysaccharidosen e.V.

At the moment we are not aware of any self-help groups.


At present we have no literature available.