During the course of our investigations, monoallelic germline RAP1B variants have been reported in patients who presented not only with thrombocytopenia, but also with additional clinical features ranging from facial dysmorphia/microcephaly and neurodevelopmental delay to abnormalities in brain, heart, kidney, and skeleton, hereafter referred to as ST: first G12V and G60R, then A59G (5, 6), and most recently, G12E (36) (see P2 to P6; Table 3). This evidence concerns the gene RAP1B and microcephaly.