Polydactyly:Clinical and molecular manifestations

Polydactyly is a malformation during the development of the human limb,which is characterized by the presence of more than the normal number of fingers or toes.It is considered to be one of the most common inherited hand disorders.It can be divided into two major groups:Non-syndromic polydactyly or syndromic polydactyly.According to the anatomical location of the duplicated digits,polydactyly can be generally subdivided into pre-,post-axial,and mesoaxial forms.Non-syndromic polydactyly is often inherited with an autosomal dominant trait and defects during the procedure of anterior-posterior patterning of limb development are incriminated for the final phenotype of the malformation.There are several forms of polydactyly,including hand and foot extra digit manifestations.The deformity affects upper limbs with a higher frequency than the lower,and the left foot is more often involved than the right.The treatment is always surgical.Since the clinical presentation is highly diverse,the treatment combines single or multiple surgical operations,depending on the type of polydactyly.The research attention that congenital limb deformities have recently attracted has resulted in broadening the list of isolated gene mutations associated with the disorders.Next generation sequencing technologies have contributed to the correlation of phenotype and genetic profile of the multiple polydactyly manifestations and have helped in early diagnosis and screening of most nonsyndromic and syndromic disorders.

Rare case of tibial hemimelia,preaxial polydactyly,and club foot

A seven-month old female presented with left tibial hemimelia(or congenital tibial aplasia; Weber type VIIb, Jones et al type 1a), seven-toed preaxial polydactyly, and severe club foot(congenital talipes equinovarus). Definitive amputation surgery disarticulated the lower limb at the knee. This case report describes the anatomical findings of a systematic post-amputation examination of the lower limb's superficial dissection, X-ray s, and computed to mography (CT) scans. From the X-rays and CT scans, we found curved and overlapping preaxial supernumerary toes, hypoplastic first metatarsal, lack of middle and distal phalanges in one supernumerary toe, three tarsal bones, hypoplastic middle phalanx and no distal phalanx for fourth toe, andno middle or distal phalanges for fifth toe. The fibula articulated with the anteromedial calcaneus and the tibia was completely absent. We identified numerous muscles and nerves in the superficial dissection that are described in the results section of the case report. Due to the rarity of this combination of anatomical findings, descriptions of such cases are very infrequent in the literature.

The Correlation between Polydactyly Phenotype and Product Quality of Beijing Fatty Chickens

[ Objective] This study aimed to investigate differences in product quality among Beijing fatty chickens with different polydactyly phenotypes. Based on the comparative analysis of production performance, egg quality and muscle quality characteristics, the correlation between polydactyly phenotype and product quali- ty of Beijing fatty chickens was analyzed, aiming at providing the reference for development and utilization of product quality and breeding of Beijing fatty chickens. [ Method] Egg laying/meat dual-purpose type Beijing fatty chickens were selected and divided into three groups （bilateral four-toed, unilateral five-toed and bilat- eral five-toed） with four replications, 60 chickens per replications, 240 chickens per group. The production performance （weight, laying rate and egg weight）, egg quality （Haugh unit） and muscle quality （pH, water-holding capacity, Warner-Bratzler shear force, TPA, nucleotide metabolites） characteristics of Beijing fatty chickens were determined. [ Result] The weight of 120-d-old and 240-d-old bilateral five-toed Beijing fatty chickens was slightly higher than that of bilateral fourtoed and unilateral five-toed Beijing fatty chickens, with no significant difference （P 〉0.05） ; egg weight of 160-d-old bilateral five-toed Beijing fatty chickens was significantly higher than that of bilateral four-toed and unilateral five-toed individuals （ P 〈 0.05 ）. Water-holding capacity of leg muscles of bilateral five-toed Bei- jing fatty chickens was significantly superior to that of unilateral five-toed and bilateral four-toed individuals （P 〈0.05 ）. The hardness, gumminess and chewiness of leg muscles of bilateral five-toed Beijing fatty chickens were significantly lower than that of unilateral five-toed and bilateral four-toed individuals （ P 〈 0.05 ）, but the coherence and elasticity were remarkably higher compared with unilateral five-toed and bilateral four-toed individuals （ P 〈 0.05 ）. Warner-Bratzler shear force of leg muscles of bilateral five-toed Beijing fatty chickens was significantly higher than that of other individuals （ P 〈 0.05 ）. There was no significant difference in flavor substances among Beijing fatty chickens with different polydactyly phenotypes （P 〉0.05）. [ Conclusion] At early stage, the weight and egg weight of fivetoed Beijing fatty chickens were slightly superior to that of four-toed individuals. In addition, Beijing fatty chickens with different polydactyly phenotypes displayed excellent muscle quality. Overall, leg muscle quality of Beijing fatty chickens exhibited a greater correlation with polydactyly phenotype than chest muscle quality.

Four-generation postaxial polydactyly in a Chinese family

Polydactyly, one of the fairly common congenital deformities of the hands and/or feet, occurs as an isolated disorder or as part of a syndrome. It is not only observed sporadically, but also inherited with a mainly autosomal dominant inheritance. However, postaxial polydactyly in both hands and feet with 24 digits in total was rarely reported in China.

Prenatal diagnosis of triphalangeal thumb-polysyndactyly syndrome by ultrasonography combined with genetic testing:A case report

BACKGROUND Triphalangeal thumb-polysyndactyly syndrome(TPT-PS)is a rare type of congenital limb deformity,and most studies focus on the genetics.Case reports of the sonographic characteristics of TPT-PS during pregnancy are rare.CASE SUMMARY A 30-year-old woman(G3P1)who had pregnancies with TPT-PS fetuses is presented.The possibility of TPT-PS was shown by ultrasound performed at the 19th wk of pregnancy,featuring hands with six metacarpals,an extra digit at the 5th finger side,and an abnormally widened thumb.Whole-exome sequencing was subsequently conducted.The results showed that exons 1-17 of the LMBR1 gene had a heterozygous duplication,with a length of approximately 253 kb.CONCLUSION We suggest prenatal ultrasound examination combined with genetic testing to diagnose TPT-PS accurately and to help clinicians and patients make decisions.

Characterization of two novel knock-in mouse models of syndromic retinal ciliopathy carrying hypomorphic Sdccag8 mutations

Mutations in serologically defined colon cancer autoantigen protein 8(SDCCAG8)were first identified in retinal ciliopathy families a decade ago with unknown function.To investigate the pathogenesis of SDCCAG8-associated retinal ciliopathies in vivo,we employed CRISPR/Cas9-mediated homology-directed recombination(HDR)to generate two knock-in mouse models,Sdccag8^(Y236X/Y236X) and Sdccag8^(E451GfsX467/E451GfsX467),which carry truncating mutations of the mouse Sdccag8,corresponding to mutations that cause Bardet-Biedl syndrome(BBS)and Senior-L?ken syndrome(SLS)(c.696T>G p.Y232X and c.1339-1340ins G p.E447GfsX463)in humans,respectively.The two mutant Sdccag8 knock-in mice faithfully recapitulated human SDCCAG8-associated BBS phenotypes such as rod-cone dystrophy,cystic renal disorder,polydactyly,infertility,and growth retardation,with varied age of onset and severity depending on the hypomorphic strength of the Sdccag8 mutations.To the best of our knowledge,these knock-in mouse lines are the first BBS mouse models to present with the polydactyly phenotype.Major phototransduction protein mislocalization was also observed outside the outer segment after initiation of photoreceptor degeneration.Impaired cilia were observed in the mutant photoreceptors,renal epithelial cells,and mouse embryonic fibroblasts derived from the knock-in mouse embryos,suggesting that SDCCAG8 plays an essential role in ciliogenesis,and cilium defects are a primary driving force of SDCCAG8-associated retinal ciliopathies.

Autopsy Findings in a Case of Ellis Van Creveld Syndrome with Review of Literature

Ellis Van Creveld (EVC) syndrome is one of the congenital anomalies not compatible with life. It is also known as chondroectodermal dysplasia. The most common manifestations of this syndrome are short ribs, postaxial polydactyly, growth retardation, and ectodermal and cardiac defects. It has an incidence of one in every 60,000 live births and equal sex predisposition. In our case, perinatal autopsy was performed in a stillborn baby of 32 weeks of gestation having syndactyly, polydactyly and short forearms to know the cause of death and the diagnosis emerged as EVC syndrome. It is important to diagnose EVC syndrome as it is transmitted as an autosomal recessive disorder, so genetic counseling is required to make parents aware of the risk of recurrence.

Current concepts in the management of the duplicated thumb

Preaxial polydactyly is a common congenital anomaly of the hand presenting at birth.Surgical treatment is aimed at creating a functional thumb capable of normal grip and pinch strength with acceptable aesthetics.Each case is unique and presents individual challenges to the hand surgeon.The aim of this review is to provide a synopsis of current knowledge and recommended surgical techniques for the duplicated thumb.