In its most severe form Hunter disease (MPS II) resembles Hurler disease, but patients do not usually have corneal clouding or a lumbar gibbus. Presentation is usually between 2 and 5 years of age, with coarse facies, recurrent respiratory infections, stunted growth or hernias. As in Hurler disease, patients have severe mental retardation, hepatosplenomegaly, stiff joints, cardiac murmurs and progressive neurological degeneration. Death usually occurs between 5 and 15 years. A milder form with normal intelligence and survival into adult life also occurs. These patients have many of the somatic features of the severe type but these are less marked and progress more slowly. Although mild patients can survive into their late 50’s or beyond and have children, sudden death at a younger age may occur from cardiac failure.
Deficiency of iduronate sulphatase is the primary defect.