Arylsulfatase B, also known as ARSB, ASB, MPS6 or G4S, is a 533 amino acid lysosomal protein that belongs to the sulfatase family. Existing as both a monomer and a homodimer, Arylsulfatase B uses calcium as a cofactor to hydrolyze C4-sulfate groups of N-Acetyl-D-galactosamine, dermatan sulfate and chondriotin sulfate, thereby playing a role in lysosomal degradation. Defects in the gene encoding Arylsulfatase B are the cause of mucopolysaccharidosis type 6 (MPS6) and multiple sulfatase deficiency (MSD), the first of which is a lysosomal storage disease that is characterized by short stature, stiff joints, skeletal malformations, corneal clouding, hepatosplenomegaly and cardiac abnormalities. In contrast, MSD is characterized by a decreased activity of all known sulfatases and is usually associated with mucopolysaccharidosis, chondrodysplasia punctata, hydrocephalus, ichthyosis and neurologic deterioration. Multiple isoforms of Arylsulfatase B exist due to alternative splicing events.