Hunter syndrome disease overview

Hunter syndrome (MPS II) is a rare, X-linked recessive disorder that affects males almost exclusively.1 Hunter syndrome is characterized by a deficiency in the activity of the lysosomal enzyme iduronate-2-sulfatase (I2S), which is one of the lysosomal enzymes responsible for degrading glycosaminoglycans (GAGs).2 Undegraded or partially undegraded GAGs progressively accumulate within tissues and organs, causing the characteristic signs and symptoms of Hunter syndrome.1,3

Different forms of Hunter syndrome (MPS II)

Two phenotypes of Hunter syndrome
Hunter syndrome has traditionally been categorized into two forms, however, the condition is better regarded as a continuum between two extremes: non-neuropathic and neuropathic (previously known as attenuated and severe, respectively).4,5

Categorization into two forms was based on clinical presentation of neurological involvement, age of onset of signs and symptoms and life expectancy, but biochemically, iduronate-2-sulfatase (I2S) activity can be equally deficient in both forms.5

References:  1. Neufeld EF, Muenzer J. In: Scriver CR, eds. The Metabolic and Molecular Bases of Inherited Disease. New York, NY: McGraw-Hill; 2001:3421-3452.  2. Wraith JE, et al. Genet Med. 2008;10(7):508-516.  3. Muenzer J et al. Pediatrics. 2007;124(6):1228-1239.  4. Giugliani R et al. Genet Mol Biol 2014; 37(2): 315-329.  5. Scarpa M et al. Orphanet J Rare Dis. 2011;6:72-89.

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