IGF2 and Pitt-Hopkins syndrome: Four variants were in responsible genes for SRS (4.3%: IGF2 in two patients, CDKN1C, and PLAG1) and five variants were in causative genes for known genetic syndromes presenting with growth failure (5.4%: IGF1R abnormality (IGF1R), SHORT syndrome (PIK3R1), Floating-Harbor syndrome (SRCAP), Pitt-Hopkins syndrome (TCF4), and Noonan syndrome (PTPN11)) (Table 1 and Additional file 2: Figure S1).