Depending on the deficient enzyme, MPS can be classified into the following 14 types: I, II, IIIA, IIIB, IIIC, IIID, IIIE (involving arylsulfatase G deficiency, encoded by the ARSG gene), IVA, IVB, VI, VII, IX, X, and the MPS-plus syndrome (MPSPS). Here, ARSG is linked to mucopolysaccharidosis-plus syndrome.