Hurler and Hunter Syndromes
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Hurler syndrome and Hunter syndrome are the lysosomal storage diseases known as the mucopolysaccharidoses. Hurler syndrome, also called mucopolysaccharidosis type I (MPS I), is caused by a deficiency of alpha-L-iduronidase. Similarly Hunter syndrome, also called mucopolysaccharidosis type II (MPSII), is caused by a deficiency of iduronate-2-sulfatase (I2S). In both diseases, the mutations lead to the accumulation of dermatan sulfate and heparan sulfate, the presence of which in body tissues leads to a variety of clinical findings. Both diseases are similar, but Hunter syndrome is a less severe form of Hurler syndrome. Hunter syndrome can be clinically differentiated by a lack of corneal clouding but with the additional finding of aggressive behavior. As an aside, Hurler syndrome was formerly known as gargoylism, as build-up of mucopolysaccharide leads to the coarsening of facial features.