Hunter syndrome is an X-linked recessive disease caused by deficiency of the lysosomal enzyme iduronate-2-sulfatase, leading to progressive accumulation of glycosaminoglycans in nearly all cell types, tissues, and organs. The estimated prevalence is 1 in 70,000 – 80,000 male live births in Europe. The disease affects males almost exclusively, although female patients have been identified.
Clinical manifestations include: Facial dysmorphism; hepatosplenomegaly; progressive airway obstruction; cardiac disease; hearing loss; loss of vision and musculoskeletal deformities. Severely affected patients also suffer from progressive cognitive dysfunction and behavioural disturbances, and have a life expectancy of less than 2 decades. The most common cause of death is airway impairment.
Enzyme replacement therapy by idursulfase may improve certain symptoms. Unfortunately, intravenously administered idursulfase does not cross the blood-brain barrier and will not alleviate neurological symptoms. It is unclear whether the potential benefits of successful stem cell transplantation outweigh the risks of this procedure.