What is Hunter syndrome (MPS II)?

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)

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