<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by X-linked infantile spasm syndrome ? [/INST] Infantile spasms are estimated to affect 1 to 1.6 in 100,000 individuals. This estimate includes X-linked infantile spasm syndrome as well as infantile spasms that have other causes. </s>