Multidisciplinary Management of Hunter Syndrome
Hunter syndrome, or mucopolysaccharidosis II, is an X-linked, progressive lysosomal storage disease in which patients are deficient in the lysosomal enzyme iduronate-2-sulfatase (I2S),1,2 which results in cellular accumulation of the glycoaminoglycans dermatan and heparan sulfate. Hunter syndrome occurs almost exclusively in males, with a reported incidence of ∼1 in 170000 male births.3 The accumulation of glycoaminoglycans within tissues and organs contributes to the Hunter phenotype, which was recently reviewed in detail by Martin et al.3 Hunter syndrome is a heterogeneous disorder, both in age at onset of symptoms and severity. Patients typically have a normal appearance at birth, with the initial signs and symptoms emerging between 18 months and 4 years of age in the severe form and ∼2 years later for those with an attenuated phenotype form.1,3,4 All patients experience somatic involvement, which can include facial dysmorphism, enlarged liver and spleen, stiff joints and contractures, cardiac valve disease, and upper-airway obstruction. The most severely affected patients, who are estimated to include ∼75% of all patients with Hunter syndrome,4 have profound neurologic involvement leading to cognitive impairment and developmental regression; death usually occurs in the second decade of life.1,3 Patients with an attenuated phenotype may have normal intelligence and typically survive into adulthood.
In 2006, Shire Human Genetic Therapies, Inc (Cambridge, MA) invited an international panel of physicians experienced in the management of patients with Hunter syndrome to discuss aspects of this metabolic disorder. The initial work of that group of experts resulted in a article that discussed the recognition and diagnosis of Hunter syndrome.3 The reader is directed to that review for a detailed presentation of the signs and symptoms of mucopolysaccharidosis II. In a subsequent meeting held in Rome, Italy, in April 2007, …
Address correspondence to Joseph Muenzer, MD, PhD, Department of Pediatrics, CB 7487, Medical School Wing E Room 117, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7487. E-mail: