<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by T-cell immunodeficiency, congenital alopecia, and nail dystrophy ? [/INST] T-cell immunodeficiency, congenital alopecia, and nail dystrophy is a rare disorder. It has been diagnosed in only a few individuals, almost all of whom are members of a large extended family from a community in southern Italy. </s>