Kaufman oculocerebrofacial syndrome (KOS) is a rare disorder affecting development and growth originally recognized 40 years ago. KOS is characterised by microcephaly, mental retardation, ocular anomalies, distinctive facial features, generalised hypotonia, and reduced growth. In this paper, exome sequencing was employed to identify UBE3B, encoding an E3 ubiquitin-protein ligase, as the gene mutated in KOS. Molecular data demonstrate that this disorder is a clinically homogeneous, recessive trait caused by UBE3B loss of function. This finding further demonstrates the impact of misregulation of protein ubiquitination on development and growth. (By Marco Tartaglia, PhD, http://jmg.bmj.com/content/early/2013/05/16/jmedgenet-2012-101405 )