<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by McKusick-Kaufman syndrome ? [/INST] This condition was first described in the Old Order Amish population, where it affects an estimated 1 in 10,000 people. The incidence of McKusick-Kaufman syndrome in non-Amish populations is unknown. </s>