It has been estimated that about 1 in 100,000 male births are affected by MPS II. Even though these diseases are rare, each individual needs such extensive medical care that the effect on the medical system is much larger than their numbers suggest. Although MPS II is individually rare, the incidence of all MPS diseases is 1 in 25,000 births and the larger family of LSDs collectively occur in about 1 in every 5,000 to 7,000 births. All families of affected individuals should seek further information from their medical/genetics doctor or from a genetic counselor if they have questions about the risk for recurrence of the disease in their family or other questions related to inheritance of MPS diseases.

http://mpssociety.org/wp-content/uploads/2011/07/booklet_MPS_II_v6.pdf