Sub-Exome Target Sequencing in a Family With Syndactyly Type IV Due to a Novel Partial Duplication of the LMBR1 Gene: First Case Report in Fujian Province of China

Genetic determinants of syndactyly: perspectives on pathogenesis and diagnosis

The formation of the digits is a tightly regulated process. During embryogenesis, disturbance of genetic pathways in limb development could result in syndactyly; a common congenital malformation consisting of webbing in adjacent digits. Currently, there is a paucity of knowledge regarding the exact developmental mechanism leading to this condition. The best studied canonical interactions of Wingless‐type–Bone Morphogenic Protein–Fibroblast Growth Factor (WNT–BMP–FGF8), plays a role in the interdigital cell death (ICD) which is thought to be repressed in human syndactyly. Animal studies have displayed other pathways such as the Notch signaling, metalloprotease and non-canonical WNT-Planar cell polarity (PCP), to also contribute to failure of ICD, although less prominence has been given. The current diagnosis is based on a clinical evaluation followed by radiography when indicated, and surgical release of digits at 6 months of age is recommended. This review discusses the interactions repressing ICD in syndactyly, and characterizes genes associated with non-syndromic and selected syndromes involving syndactyly, according to the best studied canonical WNT-BMP-FGF interactions in humans. Additionally, the controversies regarding the current syndactyly classification and the effect of non-coding elements are evaluated, which to our knowledge has not been previously highlighted. The aim of the review is to better understand the developmental process leading to this condition.

Recent Advances in Syndactyly: Basis, Current Status and Future Perspectives

A comprehensive summary of recent knowledge in syndactyly (SD) is important for understanding the genetic etiology of SD and disease management. Thus, this review article provides background information on SD, as well as insights into phenotypic and genetic heterogeneity, newly identified gene mutations in various SD types, the role of HOXD13 in limb deformities, and recently introduced modern surgical techniques for SD. This article also proposes a procedure for genetic analysis to obtain a clearer genotype-phenotype correlation for SD in the future. We briefly describe the classification of non-syndromic SD based on variable phenotypes to explain different phenotypic features and mutations in the various genes responsible for the pathogenesis of different types of SD. We describe how different types of mutation in HOXD13 cause various types of SD, and how a mutation in HOXD13 could affect its interaction with other genes, which may be one of the reasons behind the differential phenotypes and incomplete penetrance. Furthermore, we also discuss some recently introduced modern surgical techniques, such as free skin grafting, improved flap techniques, and dermal fat grafting in combination with the Z-method incision, which have been successfully practiced clinically with no post-operative complications.

Epidemiological statistics of congenital thumb duplication in the Chinese population

Background

Thumb duplication is a very common congenital malformation. This study describes and compares the phenotypic manifestations of polydactyly between southwest and northeast China. However, previous studies had a limited sample size. Therefore, this study used a large sample.

Methods

A total of 3549 well-characterized thumb duplication cases were divided into group A (southwest China) and group B (northeast China).

Results

In group A and group B, the left-to-right ratio was 1:1.5 and 1:1.75, respectively, and the female-to-male ratio was 1:1.5 and 1:1.58, respectively.

Conclusions

There were no significant differences in gender distribution or the distribution of left and right polydactyly between the two groups, but the distribution of bilateral polydactyly was significantly different.