HMGA2 and microcephaly: Published literature demonstrated relative macrocephaly in 50% PLAG1, 45.4% IGF2 and 28.5% CDKN1C. In contrast, none of the individuals with HMGA2 variants presented with relative macrocephaly, whereas the other monogenic causes had microcephaly (87.5% CDKN1C, 57.8% IGF2, 57.1% PLAG1 and 53.8% HMGA2).