<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Leigh syndrome ? [/INST] Leigh syndrome affects at least 1 in 40,000 newborns. The condition is more common in certain populations. For example, the condition occurs in approximately 1 in 2,000 newborns in the Saguenay Lac-Saint-Jean region of Quebec, Canada. </s>