<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by choroideremia ? [/INST] The prevalence of choroideremia is estimated to be 1 in 50,000 to 100,000 people. However, it is likely that this condition is underdiagnosed because of its similarities to other eye disorders. Choroideremia is thought to account for approximately 4 percent of all blindness. </s>