Hunter disease before and during enzyme replacement therapy.

Mucopolysaccharidosis type II (Hunter disease) is a lysosomal storage disease attributable to X-linked deficiency of the enzyme α-L-iduronate-sulfatase. Because of this deficiency, glycosaminoglycanes accumulate in various tissues and body fluids. We describe three patients representing the broad spectrum of Hunter disease and their response to enzyme replacement therapy. Patient 1 did not manifest central nervous system involvement, patient 2 manifested moderate neurologic disease, and patient 3 had already manifested a severe neurologic course during early infancy. In all patients, improvements in visceral organ size, physical capacity, and gastrointestinal functioning were reported. Moreover, all three patients demonstrated a gain in height, improved functioning of the upper limb, and a reduced need for antibiotics to treat upper airway infections. The response to enzyme replacement therapy occurred independent of type of genetic mutation (missense or frame shift), and we observed only mild infusion-related reactions. We conclude that all patients with mucopolysaccharidosis type II (those with and without clinical central nervous system involvement) may benefit from enzyme replacement therapy.