Although there have been rare instances where females develop MPS II, generally MPS II only occurs in males. This is because the I2S gene is located on the X chromosome. Men have one X and one Y chromosome, so a mutated I2S gene causes MPS II. Women, on the other hand, have two X chromosomes. Women are therefore carriers, but very rarely develop MPS II.
When MPS II occurs genetically, any daughter born to a woman that is a carrier will have a 50% chance of also being a carrier. Any son born to a carrier mom will have a 50% chance of developing Hunter’s Syndrome. Any daughter born to a man with MPS II will be a carrier. No son born to a man with MPS II will be affected.