<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by CHMP2B-related frontotemporal dementia ? [/INST] CHMP2B-related frontotemporal dementia has been reported in one large family in Denmark and a few unrelated individuals from other countries. This disease appears to be a rare form of frontotemporal dementia. </s>