Hunter syndrome

Hunter syndrome, or mucopolysaccharidosis type II, is an X-linked lysosomal storage disorder caused by iduronate-2-sulfatase deficiency. Its effects range from progressive neurocognitive impairment to predominantly physical disease.

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Iduronate-2-sulfatase: A lysosomal enzyme that breaks down sulfated glycosaminoglycans, including dermatan sulfate and heparan sulfate. Its deficient activity is the direct biochemical cause of Hunter syndrome.
Idursulfase: A recombinant form of iduronate-2-sulfatase used as enzyme replacement therapy for Hunter syndrome. Regular intravenous doses can reduce systemic glycosaminoglycan burden and improve some physical outcomes.
Hurler syndrome: Mucopolysaccharidosis type I, an autosomal recessive disorder caused by alpha-L-iduronidase deficiency. It can resemble Hunter syndrome clinically, but has a different enzyme defect and inheritance pattern.
Dysostosis multiplex: A characteristic pattern of skeletal abnormalities seen in several mucopolysaccharidoses and other storage disorders. Its combination of bone changes can support recognition of Hunter syndrome.
Hunter syndrome carrier testing: Genetic testing used to identify people carrying a disease-associated variant in IDS. It can clarify reproductive risks in families with an affected member.
Glycosaminoglycans: Long, repeating carbohydrate chains found in connective tissues and other parts of the body. Dermatan sulfate and heparan sulfate accumulate when the deficient enzyme cannot degrade them.
Enzyme replacement therapy: Treatment that supplies a functional version of an enzyme missing or deficient in a patient. Idursulfase treatment follows this approach, though standard dosing has limited brain access.
MPS I: The disease spectrum caused by deficient alpha-L-iduronidase, ranging from severe Hurler syndrome to attenuated forms. This related glycosaminoglycan-storage disorder helps separate enzyme-specific diagnoses.
Hepatosplenomegaly: Enlargement of the liver and spleen, often caused by disease or storage of abnormal material in tissues. Glycosaminoglycan accumulation commonly contributes to enlarged abdominal organs.
Genetic counseling: A process that explains genetic conditions, inheritance, testing options, and associated risks to individuals and families. X-linked inheritance makes family testing and reproductive decisions a central part of care.