The pathophysiology of cleft hand is thought to be a result of a wedge-shaped defect of the apical ectoderm of the limb bud (AER: apical ectodermal ridge). Polydactyly, syndactyly and cleft hand can occur within the same hand, therefore some investigators suggest that these entities occur from the same mechanism. This mechanism is not yet defined. Genetics The cause of cleft hand lies, for what is known, partly in genetics. The inheritance of cleft hand is autosomal dominant and has a variable penetrance of 70%. Cleft hand can be a spontaneous mutation during pregnancy (de novo mutation). The exact chromosomal defect in isolated cleft hand is not yet defined. However, the genetic causes of cleft hand related to syndromes have more clarity. The identified mutation for SHSF syndrome (split-hand/split-foot syndrome) a duplication on 10q24, and not a mutation of the tp63 gene as in families affected by EEC syndrome<unk> –ectodermal dysplasia–cleft syndrome). The p63 gene plays a critical role in the development of the apical ectodermal ridge (AER), this was found in mutant mice with dactylaplasia. Embryology Some studies have postulated that polydactyly, syndactyly and cleft hand have the same teratogenic mechanism. In vivo tests showed that limb anomalies were found alone or in combination with cleft hand when they were given Myleran. These anomalies take place in humans around day 41 of gestation.
Ectrodactyly
Clinodactyly
Synpolydactyly
Sclerodactyly
Syndactyly
Camptodactyly
Oligodactyly
Pachydermodactyly