Embryology of normal web space creation and the genetics of syndactyly in humans and experimental animals are well described in the literature. In this review, the author offers a 3-step pathway of pathogenesis for syndactyly. The first step is initiated either by the overactivation of the WNT canonical pathway or the suppression of the Bone Morphogenetic Protein (BMP) canonical pathway. This leads to an overexpression of Fibroblast Growth Factor 8 (FGF8). The final step is the suppression of retinoic acid in the interdigital mesenchyme leading to suppression of both apoptosis and extracellular matrix (ECM) degradation, resulting in syndactyly.

Fibroblast growth factors (FGFs) are diffusible polypeptides released by a variety of cell types. FGF8 subfamily members regulate embryonic development processes through controlling progenitor cell growth and differentiation, and are also functional in adults in tissue repair to maintain tissue homeostasis. FGF8 family members exhibit unique binding affinities with FGF receptors and tissue distribution patterns. Increasing evidence suggests that, by regulating multiple cellular signaling pathways, alterations in the FGF8 subfamily are involved in craniofacial development, odontogenesis, tongue development and salivary gland branching morphogenesis. Aberrant FGF signaling transduction, caused by mutations as well as abnormal expression or isoform splicing, plays an important role in the development of oral diseases. Targeting FGF8 subfamily members provides a new promising strategy for the treatment of oral diseases. The aim of this review was to summarize the aberrant regulations of FGF8 subfamily members and their potential implications in oral‑maxillofacial diseases.

Two main types of cleft hands have been described. The ulnar cleft hand deformity is very rare and is characterized by two constant features: a deep cleft radial to the little finger and hypoplasia of the ulnar digits. The pathogenesis of ulnar clefts is unknown. The second type is the central cleft hand deformity, which is characterized by a soft tissue/bone defect in the hand centrally. Patients with central clefts also have several concurrent deformities in the remaining digits. This paper reviews the clinical features of three cases with ulnar cleft hands and 44 cases of central cleft hands, with special emphasis on concurrent deformities. The author\'s hypothesis of pathogenesis for both types of clefts and their concurrent deformities is then offered.

Agnathia (otocephaly) is a sporadic malformation characterized by agenesis of the mandible with characteristic dysmorphologic sequelae. We compare the prenatal presentations and dysmorphologic abnormalities of 2 female fetuses with agnathia. Fetus 1 was delivered at 33 weeks\' gestational age and showed agnathia with characteristic sequelae of microstomia; microglossia; persistent buccopharyngeal membrane; and ventrally placed, malformed external ears. Fetus 2 was delivered at 32 weeks\' gestational age and exhibited agnathia, astomia, and microglossia; in contrast to fetus 1, however, the external ears were laterally placed, low set, and malformed. For both fetuses, tridimensional computed tomographic scan showed the unique complete absence of the mandible. Additional malformations were documented and differed between the fetuses. We discuss the current molecular mechanisms implicated in 1st branchial arch patterning, particularly the impact of bone morphogenetic protein and fibroblast growth factor 8, and how these findings have the potential to explain the spectrum of abnormalities present in these 2 fetuses with agnathia without associated holoprosencephaly.