Microduplication 22q11.2 syndrome: A syndrome due to duplication of a tiny part of chromosome band 22q11.2. Features of the syndrome include the appearance of widely spaced eyes and superior placement of eyebrows; downslanting palpebral fissures (eye slits); mild micrognathia (small chin) and retrognathia (recessed chin); and a long, narrow face. The microduplication arises because chromosome band 22q11.2 is predisposed to rearrangement due to misalignment of what are called low-copy repeats -- a small number of adjacent copies of an identical pattern of nucleotides in the DNA. The microduplication may be detected by interphase fluorescence in situ hybridization (FISH). The size of the microduplications range from 34 Mb to 6 Mb.