All forms of mucopolysaccharidosis type I (MPS I) are a spectrum of the same disease. Hurler-Sheie is the subtype of MPS I with intermediate severity. Hurler syndrome is the most severe form, while Scheie syndrome is the least severe form. Some clinicians consider the differences between Hurler, Hurler-Scheie, and Scheie syndromes to be arbitrary. Instead, they classify these patients as having "severe", "intermediate", or "attenuated" MPS I.[1]