Overview of the 1q21.1 microduplications described in this study and those reported by Mefford et al.13 and Brunetti-Pierri et al.14 The 1q21.1 microduplications containing the distal 1q21.1q21.2 region can be divided into two classes: class I, containing only the distal region, and class II, containing both the thrombocytopenia with absent radius (TAR)-associated 1q21.1 region and the distal 1q21.1q21.2 region. The TAR-associated 1q21.1 region is highlighted in red. Both the minimal regions for the class I and class II regions are highlighted in green. The minimal duplicated region in patients 1 and 2 is highlighted in blue. The blocks of segmental duplications are shown at the bottom. All coordinates are given in GRCh37.