What unique feature is present in Hurler syndrome that is absent in Hunter syndrome?

The unique feature that is present in Hurler syndrome and is absent in Hunter syndrome is corneal clouding. Hurler syndrome, which is the more severe form of mucopolysaccharidosis type I, is characterized by a range of symptoms including developmental delays, skeletal abnormalities, and distinctive facial features often described as "gargoylism." One prominent clinical manifestation in Hurler syndrome is the presence of corneal clouding, which can lead to impaired vision due to the accumulation of glycosaminoglycans in the cornea.

In contrast, while both Hurler and Hunter syndromes involve intellectual disabilities and have overlapping features like gargoylism and joint stiffness, corneal clouding specifically distinguishes Hurler syndrome from Hunter syndrome. In Hunter syndrome, which is a milder form and is X-linked, corneal clouding does not occur, further differentiating the two conditions. This distinction is important for diagnosis and management of these lysosomal storage disorders.