MPS II has an X-linked recessive pattern of inheritance. Since<unk>  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. 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.
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