MPS III A. Sanfilippo A disease.
Incidence
1:24,000 for all the types. AR inheritance. It is a Heparan N-sulfamidase deficiency. Type A is the more severe of the different sub-types.
Clinical Characteristics
Severe mental retardation, mild skeletal changes, corneal clouding questionable (nearly always absent). There is very little coarsening features in Sanfilippo disease. Minimal dwarfism. No cardiac abnormalities. Progressive neurological deterioration with seizures & athetosis Mild bone changes. No visceral involvement. Before age 10 years, ambulation is no longer possible and patients are confined to bed. The course is inexorably progressive and most patients die before age 20 yrs. It should be noted that 26% of the patients with MPS IIIA had normal early developmental milestones and the average onset of regression (speech, motor, cognitive) was 3.3 years of age (Meyer et al. 2007). Of note, those patients with the p.Ser298Pro mutation on one allel (which is associated with a slower progression of the disease) had their onset of regression (speech, motor, cognitive) 2.6 years later than the rest of the cohort with different genotypes whose regression started at 2.8 +/- 1.1 years (Meyer et al, 2008).
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
EB(F), Urine metabolic screen with Berry test. MPS (HS) in urine. Frequently the spot test may be false negative.