Coffin-Siris syndrome (CSS) is a rare congenital multi-systemic genetic disorder characterised by aplasia or hypoplasia of the distal phalanx or nail of the fifth digit, developmental delay, intellectual disability, coarse facial features, hypotonia, microcephaly, sacral dimple, spina bifida occulta, scoliosis/kyphosis, cleft palate, macroglossia, micrognatia, chronic respiratory upper infections, cardiac abnormalities and gastroesophageal reflux. More than 100 cases of confirmed CSS have been clinically and/or genetically reported to date. Until now, at least seven responsible genes for CSS have been identified; SMARCB1, SMARCA4, SMARCE1, ARID1A, ARID1B, SOX11, and PHF6. The inheritance mode of CSS by these genes is autosomal dominant. The exact prevalence and incidence are not known, but the disorder is probably under-recognised.