Sanfilippo syndrome or mucopolysaccharidosis type III is a rare hereditary neuro-metabolic disease, a genetic error of metabolism.
Mucopolysaccharides are long chains of sugar molecules, which are used in the construction of connective tissues.
When the body has finished using these molecules, it breaks them down with enzymes, then recycles or eliminates them. Children with Sanfilippo syndrome lack or are deficient in the enzyme that breaks down these molecules, so the body stores them.
This storage causes progressive damage in various tissues, leading to a general impairment of all the body’s vital functions; in particular, the accumulation of these molecules in the brain leads to progressive intellectual disability and loss of motor function.
There are four different types of Sanfilippo syndrome.
Each type is named according to the type of missing or defective enzyme.
It is the most common type and is also considered the most severe, with earlier death than the other types. These children are deficient in the enzyme Heparan N-sulfatase.
It is the result of a deficiency of
It is caused by a deficiency of acetyl-CoAlpha-glucosaminide acetyltransferase.
It is caused by a deficiency of N-acetylglucosamine 6-sulphatase
It is an autosomal recessive hereditary disease, meaning that both parents must be carriers for the child to be affected.
There is a one in two (50%) chance that carrier parents will have healthy children who are also carriers. While the probability of carrier parents having healthy non-carrier children is one in four (25%). The probability of carrier parents having sick children is also one in four (25%).
Sanfilippo syndrome is a progressive disease: at birth, children appear normal and show no signs of the disorder. The onset of the disease occurs around 2-4 years of age, with symptomatology consisting of behavioural disorders (hyperkinesia, aggressiveness) and mental deterioration, sleep disturbances, and very mild dysmorphisms.
Depending on the forms of Sanfilippo, neurological degeneration occurs well before the age of 10, often with loss of intellectual abilities acquired in the very early years.
The most severe form is IIIA, although some patients with attenuated forms have been described. Forms IIIB and IIID are the most heterogeneous as manifestations, while form IIIC is intermediate to the latter.