Congenital malformations or complex malformation syndromes are frequently associated with growth failure and have been the subject of much research and discussion in the paediatric literature. The less common overgrowth syndromes (OGSs) have until recently received little attention. The disordered growth in OGSs is, however, a primary anomaly and, unlike growth failure, is not explained away as a secondary phenomenon as is the case with many other complex syndromes. OGSs may therefore provide a fascinating window into the mechanisms of growth and the consequences of the failure of this regulation.

Ancient literature has many references to giants such as Goliath, Polyphemus, Gargantua, or the Patagonian giants. Whether real or fictional, these reports show that such patterns have been present throughout history and serve to highlight two of the central issues—what is a “true overgrowth syndrome and how many overgrowth syndromes exist?”

Previously, overgrowth patterns were often categorised as primary or secondary. In primary disorders, the growth would be an intrinsic (unexplained) feature of the condition secondary to cellular hyperplasia, whereas in secondary disorders an identifiable cause, often endocrinological, would be expected to result in growth excess.1 The limitations of this rather simplistic differentiation have been illustrated by the identification of “novel” growth factors in a number of OGSs, such as Beckwith-Wiedemann syndrome (BWS) and Simpson-Golabi-Behmel syndrome (SGBS). In these disorders, abnormalities of insulin-like growth factor II (IGF II) and glypican 3 have been implicated.2 3 It would seem that if the term secondary growth excess is still relevant, it should be limited to situations dependent on extrinsic growth promoters, such as fetal macrosomia secondary to maternal diabetes and hyperglycaemia and subsequent fetal hyperinsulinaemia. For the foreseeable future most “primary” OGSs will be classified by a process of clinical assessment and/or laboratory exclusion with the possible exceptions of BWS …