SGSH and mucopolysaccharidosis type 3A: Mucopolysaccharidosis type IIIA (MPS IIIA) is an autosomal recessive LSD due to a mutation in the gene of N-sulfoglucosamine sulfohydrolase (SGSH) that causes a lack of activity of this enzyme, involved in the degradation of the glycosaminoglycan heparan-sulfate.