question: What are the 4 types of holoprosencephaly?
answer: Holoprosencephaly is a rare congenital disorder which results from failure of cleavage or incomplete differentiation of the forebrain structures at various levels or to various degrees . Depending on the degree of involvement, it is classified into 4 types: Alobar, Semilobar, Lobar, and Middle interhemispheric fusion variant .