Females generally have two X chromosomes, whereas males generally have one X chromosome that they inherit from their mother and one Y chromosome that they inherit from their father.If a female inherits one copy of the mutant allele for MPS II, she will usually have a normal copy of the IDS gene which can compensate for the mutant allele. This is known as being a genetic carrier. A male who inherits a defective X chromosome, though,  usually does not have another X chromosome to compensate for the mutant gene. Thus, a female would need to inherit two mutant genes to develop MPS II, while a male patient only needs to inherit one mutant gene. A female carrier can be affected due to X-inactivation, which is a random process. Pathophysiology
The human body depends on a vast array of biochemical reactions to support critical functions. One of these functions is the breakdown of large biomolecules. The failure of this process is the underlying problem in Hunter syndrome and related storage disorders.The biochemistry of Hunter syndrome is related to a problem in a part of the connective tissue known as the extracellular matrix, which is made up of a variety of sugars and proteins. It helps to form the architectural framework of the body. The matrix surrounds the cells of the body in an organized meshwork and functions as the glue that holds the cells of the body together. One of the parts of the extracellular matrix is a molecule called a proteoglycan.
If carpal tunnel syndrome develops, a further decrease in hand function can occur. The bones themselves may be affected, resulting in short stature. In addition, pebbly, ivory-colored skin lesions may be found on the upper arms, legs, and upper back of some people with it. These skin lesions are considered pathognomic for the disease. Finally, the storage of GAGs in the brain can lead to delayed development with subsequent intellectual disability and progressive loss of function.The age at onset of symptoms and the presence or absence of behavioral disturbances are predictive factors of ultimate disease severity in very young patients. Behavioral disturbances can often mimic combinations of symptoms of attention deficit hyperactivity disorder, autism, obsessive compulsive disorder, and/or sensory processing disorder, although the existence and level of symptoms differ in each affected child. They often also include a lack of an appropriate sense of danger, and aggression. The behavioral symptoms of MPS II generally precede neurodegeneration and often increase in severity until the mental handicaps become more pronounced. By the time of death, most children with severe MPS II have severe mental disabilities and are completely dependent on their caretakers. Genetics
Since Hunter syndrome is an X-linked recessive disorder, it preferentially affects male patients. The IDS gene is located on the X chromosome. The IDS gene encodes for an enzyme called iduronate-2-sulfatase (I2S). A lack of this enzyme leads to a buildup of GAGs, which cause the symptoms of MPS II.