Yes, it is genetic. MPS II is the result of a gene mutation to the I2S gene.  In most cases, this mutation is genetically determined. However, it is also possible that the mutation occurs during egg and sperm formation (which is what happened to make me a carrier…no one else in my family is a carrier). In this rare instance, the mutation is not genetic and the chance of the mutation occurring in subsequent generations is low.

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.