<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Aicardi syndrome ? [/INST] Aicardi syndrome is a very rare disorder. It occurs in about 1 in 105,000 to 167,000 newborns in the United States. Researchers estimate that there are approximately 4,000 affected individuals worldwide. </s>