Syndactyly: phenotypes, genetics and current classification

Comparison Between Surgical Techniques for Correction of Congenital Syndactyly: A Systematic Review and Meta Analysis

This review aimed to assess which surgical technique has better outcomes to correct one of the most common congenital anomalies of the upper limb: syndactyly. The following databases were used in the search: PubMed, Embase, Cochrane (CENTRAL), LILACS, SciELO, Scopus and Web of Science, on October 27, 2022. Studies that described a surgical technique for correcting syndactyly and evaluated surgical complications were included. Studies about noncongenital or foot syndactyly were excluded. The risk of bias was assessed using a specific method for case reports. For synthesis of results, the characteristics of the studies and techniques were demonstrated by a qualitative analysis. Meta-analysis models were applied for complications, functionality, and aesthetic. 73 studies were included, of which 70 were series or case reports, 27 studies did not use skin grafts and 7 studies used external fixators. To evaluate functional results, 42 studies used only the surgeon's opinion. Meta-analyses showed a higher incidence of scar defects when using skin grafts and of infection when using external fixators. There was no difference for web creep and readmission. Few studies evaluated results using the VSS scale, showing worse scar pigmentation when skin grafts were used, but there was no difference in other parameters (PROSPERO CRD42022368930).

Graftless Syndactyly Release

Syndactyly release aims to address skin deficits by resurfacing web spaces and sides of digits to allow independent digital motion while minimizing the risk of web creep and scar contractures. Conventional methods include the use of a dorsal and interdigitating flaps with full-thickness skin grafts. More recently, there have been several descriptions of "graftless" syndactyly release without skin grafts, thus avoiding a further (usually distant) donor site. However, the indications of when and when not to use these techniques remain unclear. In addition, the inevitable scarring from extra recruitment of local adjacent skin is perhaps underemphasized. In this article, we revisit the trilobed flap technique which serves to balance the amount of skin needed for resurfacing digits while minimizing local donor site scarring. The geometry and nuances of the flap inset are illustrated in detail to guide those embarking on this technique. The trilobed syndactyly release technique is a reproducible, safe, and reliable method for the release of simple syndactyly.

The pathogenic mechanism of syndactyly type V identified in a Hoxd13Q50R knock-in mice

Syndactyly type V (SDTY5) is an autosomal dominant extremity malformation characterized by fusion of the fourth and fifth metacarpals. In the previous publication, we first identified a heterozygous missense mutation Q50R in homeobox domain (HD) of HOXD13 in a large Chinese family with SDTY5. In order to substantiate the pathogenicity of the variant and elucidate the underlying pathogenic mechanism causing limb malformation, transcription-activator-like effector nucleases (TALEN) was employed to generate a Hoxd13Q50R mutant mouse. The mutant mice exhibited obvious limb malformations including slight brachydactyly and partial syndactyly between digits 2-4 in the heterozygotes, and severe syndactyly, brachydactyly and polydactyly in homozygotes. Focusing on BMP2 and SHH/GREM1/AER-FGF epithelial mesenchymal (e-m) feedback, a crucial signal pathway for limb development, we found the ectopically expressed Shh, Grem1 and Fgf8 and down-regulated Bmp2 in the embryonic limb bud at E10.5 to E12.5. A transcriptome sequencing analysis was conducted on limb buds (LBs) at E11.5, revealing 31 genes that exhibited notable disparities in mRNA level between the Hoxd13Q50R homozygotes and the wild-type. These genes are known to be involved in various processes such as limb development, cell proliferation, migration, and apoptosis. Our findings indicate that the ectopic expression of Shh and Fgf8, in conjunction with the down-regulation of Bmp2, results in a failure of patterning along both the anterior-posterior and proximal-distal axes, as well as a decrease in interdigital programmed cell death (PCD). This cascade ultimately leads to the development of syndactyly and brachydactyly in heterozygous mice, and severe limb malformations in homozygous mice. These findings suggest that abnormal expression of SHH, FGF8, and BMP2 induced by HOXD13Q50R may be responsible for the manifestation of human SDTY5.

Epidemiology of congenital polydactyly and syndactyly in Hunan Province, China

OBJECTIVE

To describe the prevalence and epidemiology of congenital polydactyly and syndactyly in Hunan Province, China, 2016-2020.

METHODS

Data were obtained from the Birth Defects Surveillance System in Hunan Province, China, 2016-2020. Prevalence of birth defects (polydactyly or syndactyly) is the number of cases per 1000 births (unit: ‰). Prevalence and 95% confidence intervals (CI) were calculated by the log-binomial method. Chi-square trend tests (χ2trend) were used to determine trends in prevalence by year. Crude odds ratios (ORs) were calculated to examine the association of each demographic characteristic with polydactyly and syndactyly.

RESULTS

Our study included 847,755 births, and 14,459 birth defects were identified, including 1,888 polydactyly and 626 syndactyly cases, accounting for 13.06% and 4.33% of birth defects, respectively. The prevalences of total birth defects, polydactyly, and syndactyly were 17.06‰ (95%CI: 16.78-17.33), 2.23‰ (95%CI: 2.13-2.33), and 0.74‰ (95%CI: 0.68-0.80), respectively. Most polydactyly (96.77%) and syndactyly (95.69%) were diagnosed postnatally (within 7 days). From 2016 to 2020, the prevalences of polydactyly were 1.94‰, 2.07‰, 2.20‰, 2.54‰, and 2.48‰, respectively, showing an upward trend (χ2trend = 19.48, P < 0.01); The prevalences of syndactyly were 0.62‰, 0.66‰, 0.77‰, 0.81‰, and 0.89‰, respectively, showing an upward trend (χ2trend = 10.81, P = 0.03). Hand polydactyly (2.26‰ vs. 1.33‰, OR = 1.69, 95%CI: 1.52-1.87) and hand syndactyly (0.43‰ vs. 0.28‰, OR = 1.42, 95%CI: 1.14-1.76) were more common in males than females. Polydactyly (2.67‰ vs. 1.93‰, OR = 1.38, 95%CI: 1.26-1.51) and syndactyly (0.91‰ vs. 0.62‰, OR = 1.47, 95%CI: 1.26-1.72) were more common in urban areas than in rural areas. Compared to maternal age 25-29, hand polydactyly was more common in maternal age < 20 (2.48‰ vs. 1.74‰, OR = 1.43, 95%CI: 1.01-2.02) or ≥ 35 (2.25‰ vs. 1.74‰, OR = 1.30, 95%CI: 1.12-1.50).

CONCLUSION

In summary, we have described the prevalence and epidemiology of polydactyly and syndactyly from hospital-based surveillance in Hunan Province, China, 2016-2020. Our findings make some original contributions to the field, which may be valuable for future research.

A novel homozygous missense variant in LRP4 causing Cenani-Lenz syndactyly syndrome and literature review

BACKGROUND

Cenani-Lenzsyndactyly syndrome (CLSS; OMIM 212780) is a rare autosomal recessive acral deformity, which is mainly manifested in the fusion of fingers or toes, disordered phalangeal structure, shortening or fusion of the radius and ulna, and renal hypoplasia.

CASE PRESENTATION

Our report described an individual with mild phenotypes from China. His parents were not consanguineous. The affected individual was non-dysmorphic. Standard X-ray showed that the both hands have only four metacarpal bones. The distal end of the first metacarpal bone on the right was relatively slender, and the distal phalanx was absent. Multiple phalanges and some soft tissues of both hands were fused. Exome sequencing revealed a novel biallelic c.282C⟩Avariant in low-density lipoprotein receptor-related protein 4 (LRP4; OMIM604270; NM_002334.4) causing p. (Asn94Lys) change in the encoded protein. This variant is predicted to be potentially pathogenic, affecting protein structure and function.

CONCLUSION

We report a novel missense variant present in homozygosity in LRP4 to broaden the pathogenic spectrum of LRP4 in syndactyly, and exome sequencing technology is a powerful tool for genetic analysis in prenatal diagnosis and medical research, as a preferred method for the diagnosis of syndactyly and related phenotypes.

Postnatal diagnosis of congenital anomalies despite active systematic prenatal screening policies: a population-based registry study

BACKGROUND

Prenatal screening for congenital anomalies is an important component of maternity care, with continual advances in screening technology. However, few recent studies have investigated the overall effectiveness of a systematic policy of prenatal screening for congenital anomalies, such as in France where an ultrasound per trimester is recommended for all pregnant individuals.

OBJECTIVE

This study aimed to assess the proportion and the type of congenital anomalies that are not detected during pregnancy.

STUDY DESIGN

The study population included all singleton fetuses and newborns with congenital anomalies from the Paris Registry of Congenital Malformations (remaPAR) from 2001 to 2021. The registry includes all live births and stillbirths at ≥22 weeks of gestation and terminations of pregnancy for fetal anomaly at any gestational age with congenital anomalies diagnosed from the prenatal period until discharge home from hospital after birth. The prevalence of postnatally detected congenital anomalies was estimated overall and for 5-year intervals within the study period. We also reported the proportion of postnatal detection by subgroups of congenital anomalies according to the EUROCAT classification.

RESULTS

Of the 16,602 malformed singleton fetuses and newborns, 32.7% were detected postnatally. Of those with severe anomalies, 11.9% were detected postnatally. The postnatal detection rate decreased from 34.3% from 2001 to 2005, to 27.8% from 2016 to 2021 (P<.001). Anomalies most frequently detected postnatally were genital anomalies (n=969; 87.0%), followed by ear, neck, and face anomalies (n=71; 78.0%), eye anomalies (n=154; 74.0%), and limb anomalies (n=1802; 68.4%). Anomalies of the kidneys and the urinary tract (n=219; 7.1%) and the abdominal wall (n=37; 8.7%) were least likely to be detected after birth. Among the anomalies classified as severe, postnatal detection rates were highest for limb reduction defects (n=142; 40.6%), complete transposition of the great arteries (n=31; 17.6%), and diaphragmatic hernia (n=26; 17.2%).

CONCLUSION

Despite improvement of prenatal screening over a 20-year period, our results show that there is still a margin for improvement in prenatal diagnosis of congenital anomalies.

A Complex Case of Clino-Syndactyly with Fourth Metacarpal Aplasia

Syndactyly is the most common congenital malformation of the hand, leading to the fusion of the digits and frequently affecting the ring and middle fingers. The incidence is 1 out of 2500 children, predominantly occurring in boys and Caucasians. Clinically, the malformation may present as a soft tissue or bony fusion, resulting in the union of the fingers characterised as complete or incomplete. This fusion may involve the phalanges but may also extend to the carpal/tarsal bones, even to the metacarpal or metatarsal level, rarely to the distal end of the forearm and lower leg. The malformation is mostly isolated but may occur together with other disorders or malformations such as synostosis, acro-syndactyly, cleft hand, clinodactyly, or polydactyly. Syndromic syndactyly can be observed in cases of Apert syndrome, Poland's syndrome, Pfeiffer syndrome, and many others. A girl born in June of 2019 was diagnosed with congenital malformation of the right hand at birth-affecting the right middle, ring, and little fingers, respectively. After X-ray imaging, the fusion of the third and fourth proximal phalanges to a common metacarpal was identified, forming a unique diagnosis of clino-syndactyly with metacarpal aplasia. Surgical intervention was advocated for, including a wedge osteotomy to correct the synchondrosis at the phalangeal base and a dorsal flap to close the interdigital space created during the correction of the III and IV. fingers. A trapezoid flap for the release of the syndactyly of the IV and V. fingers was applied. The paper aims to present this surgical correction and its results regarding an atypical case of syndactyly with clinodactyly and metacarpal aplasia.

Sequence Variants in MEGF8 and GJA1 Underlying Syndactyly

Introduction

Syndactyly is a common congenital limb malformation. It occurs due to embryological failure of digit separation during limb development. Syndactyly often runs in families with an incidence of about one out of every 2,500-3,000 live births.

Methods

Here, we have reported two families presenting features of severe forms of syndactyly. The disorder segregated in autosomal recessive in one and in autosomal dominant manner in the second family. Search for the causative variants was carried out using whole-exome sequencing in family A and candidate gene sequencing in family B.

Results

Analysis of the sequencing data revealed two novel missense variants, including p.(Cys1925Arg) in MEGF8 in family A and p.(Thr89Ile) in GJA1 in family B.

Conclusion

In conclusion, the novel findings, presented here, not only expand the mutation spectrum in the genes MEGF8 and GJA1, but this will also facilitate screening other families carrying similar clinical features in the Pakistani population.

The changing epidemiology of syndactyly in Chinese newborns: a nationwide surveillance-based study

BACKGROUND

Little is known about the epidemiologic features of syndactyly (SD) in Chinese newborns.

METHODS

Using 2007-2019 data from the Chinese Birth Defects Monitoring Network, we conducted a prevalence analysis on overall, isolated and associated syndactyly according to birth year, maternal age, maternal residence, geographic region and infant sex, with special interests in time trends, perinatal outcomes and clinical phenotypes.

RESULTS

A total of 13,611 SD cases were identified among 24,157,719 births in the study period, yielding the prevalence of 5.63, 4.66 and 0.97 per 10,000 for overall, isolated, and associated SD, respectively. The prevalence of each type of SD exhibited an upward trend over the period. The prevalence of overall SD varied significantly by maternal residence (urban vs. rural, 6.69/10,000 vs. 4.35/10,000), maternal age (< 20 years, 5.43/10,000; 20-24 years, 5.03/10,000; 25-29 year, 5.65/10,000; 30-34 years, 6.07/10,000; ≥ 35 years, 5.76/10,000), geographic region (central, 5.07/10,000; east, 6.75/10,000; west, 5.12/10,000), and infant sex (male vs. female, 6.28/10,000 vs. 4.86/10,000). Newborns with associated SD were more likely to be born prematurely (29.2% vs. 10.6%) or with low birthweight (30.5% vs.9.8%) than those with isolated SD. The bilaterally, and unilaterally affected cases accounted for 18.4% and 76.7%, respectively. The feet were more frequently involved (64.3%) in those bilaterally affected cases, while right side preference (right vs left: 53.8% vs 46.2%) and upper limbs preference (hand vs foot: 50.8% vs 48.0%) were found in unilateral cases.

CONCLUSIONS

The prevalence of syndactyly in China is on the rise and notably higher than that in other Asian and European countries, highlighting the importance of investigating the etiology, epidemiology, and clinical implications of this condition in the Chinese population.

A newborn male with Myhre syndrome, hearing loss, and complete syndactyly of fingers 3-4

BACKGROUND

Myhre syndrome is a rare multisystem genetic disorder that is caused by de novo heterozygous gain-of-function variants in SMAD4. Patients with Myhre syndrome exhibit several phenotypes at different ages such as small size, autism, developmental delay, left-sided heart defects, and hearing loss and often have a characteristic facial appearance. The early clinical diagnosis of Myhre syndrome remains a major challenge, particularly in the first year of life.

METHODS

A Chinese male infant with syndactyly of fingers, hypertelorism, short palpebral fissures, and short philtrum was enrolled into the ENT department of the Chinese PLA General Hospital. Whole exome sequencing analysis was used to detect the disease-causing variant. A literature review of Myhre syndrome was also performed.

RESULTS

A recurrent de novo missense variant c.1498A > G p.I500V(p. Ile500Val) in SMAD4 was detected confirming the clinical diagnosis of Myhre syndrome at the age of 38 days. The infant appears to be the youngest reported case of Myhre syndrome. At 23-month follow-up, the affected infant has dysmorphic facial features, growth retardation, and previously undescribed complete syndactyly. Review the literatures noted several common features in Myhre syndrome patients including hearing loss (72.7%), characteristic facial features (26.0%-54.5%), finger and toe abnormalities (3.9%-48.1%), short stature (45.5%), and respiratory (30.0%) and cardiovascular problems (65.0%).

CONCLUSIONS

Clinicians should have a low threshold to perform genetic testing on patients with features suggesting Myhre syndrome even in the first year of life. Although some individuals with Myhre syndrome have normal hearing, early onset or progressive hearing loss usually occur in one or both ears in most patients, with remarkable phenotypic heterogeneity. Syndactyly may be minor such as typical 2-3 toe involvement, or more complicated as was observed in our patient.

Fetal Hands: A Comprehensive Review of Prenatal Assessment and Diagnosis Over the Past 40 Years

Fetal skeletal dysplasias involving limbs and hands are rare congenital malformations. Prenatal two-dimensional ultrasound diagnosis of fetal limb defects has a sensitivity of about 30%; however, an increased detection rate may be obtained using three-dimensional (3-D) ultrasound in the rendering mode. 3-D ultrasound may be used as a complementary method providing additional information. Currently, magnetic resonance imaging (MRI), with the emergence of ultrafast imaging techniques and new sequences, allows for better diagnosis of several fetal skeletal dysplasias such as limb reduction defects and neuromuscular disorders. 3-D volumetric images from ultrasound or MRI scan data allow 3-D ultrasound reconstructions of virtual/physical models, and virtual reality can help researchers to improve our understanding of both normal and abnormal fetal limb/hand anatomy. In this article, we review the embryological development of fetal hands and their main anomalies including prenatal diagnostic methods, genetic counseling, the role of orthopedic and plastic surgery reconstruction, and new perspectives in fetal surgery.

Syndactyly in the Pediatric Population: A Review of the Literature

Syndactyly is one of the most common congenital upper extremity deformities. Syndactyly can be described as either simple, involving just the skin and soft tissue, or complex, involving the phalanges. Additionally, syndactyly can be categorized as complete, involving the entire digit (including the nail fold), or incomplete, which does not involve the nail fold. Multiple familial or spontaneous genetic abnormalities can cause syndactyly, and these mutations typically involve the canonical wingless-type (WNT) pathway. Surgical repair of syndactyly is typically done between six to 18 months of age, depending on the type of syndactyly. Regardless of the classification of the syndactyly, the repair is performed before school-going age (except in the case of extremely mild or rare, extremely complex syndactyly). One or more imaging modalities are used to aid the surgeon in deciding the surgical approach for the syndactyly repair. The surgical plan must be clearly communicated with parents to manage expectations of aesthetics and function of the digits post-surgery. In brief, a syndactyly release surgery involves the creation of the web space using a geometrical design of the surgeon's choice, defatting of finger flaps, separation of the digits, and closure with absorbable sutures. However, the approach may vary depending on the patient. A "best" approach for rectifying the difference in surface area of separated versus fused digits has not yet been determined. While this was typically done using a skin graft, the use of alternative methods (most notably, using a synthetic dermal substitute or not using a graft at all and allowing the skin to heal with secondary intention) has been on the rise given the undesirable side effects of a graft. Less commonly, an external fixator can be used to expand soft tissue and skin. In the case of complete syndactyly, the Buck-Gramcko technique is most commonly used for nail flap reconstruction. Complications of the surgery include contracture, web creep, and the need for a second surgery. Thus, parents must be counseled in recognizing signs of complications.

A novel variant in AFF3 underlying isolated syndactyly

Isolated syndactyly is a common limb malformation with limited known genetic etiology. We used exome sequencing to discover a novel heterozygous missense variant c.2915G > C: p.Arg972Pro in AFF3 on chromosome 2q11.2 in a family with isolated syndactyly in hands and feet. AFF3 belongs to a family of nuclear transcription activating factors and is involved in limb dorsoventral patterning. The variant Arg972Pro is located near the C terminus, a region that is yet to be associated with human disorders. Functional studies did not show a difference in the stability or subcellular localization of the mutant and wild type proteins. Instead, overexpression in zebrafish embryos suggests that Arg972Pro is a loss-of-function allele. These results suggest that variants in the C terminus of AFF3 may cause a phenotype distinct from previously characterized AFF3 variants.

Keeping you on your toes: Smith-Lemli-Opitz Syndrome is an easily missed cause of developmental delays

Smith-Lemli-Opitz syndrome (SLOS) is a relatively common genetic cause of developmental delay and may only present in conjunction with 2,3 toe syndactyly. This case series illustrates a milder phenotype of SLOS, where the predominant findings are neurocognitive in the presence of 2,3 toe syndactyly.

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 non-syndromic and syndromic disorders.

Novel mutations in GJA1 in two Brazilian families with oculodentodigital dysplasia

Oculodentodigital dysplasia (ODDD; MIM #164200), a rare genetic disorder characterized by abnormal craniofacial, dental, ocular, and digital features, is caused by mutations in GJA1 (gap junction alpha-1) gene and inherited in an autosomal dominant pattern. However, an autosomal recessive pattern is also reported. Here we described 2 families with members affected by ODDD. In the first family, the c.752G>C (p.S251T) and c.848C>T (p.P283L) heterozygous missense mutations and the c.825C>T (p.T275T) silent mutation were identified in the proband, which showed mild ODDD phenotypes, and in his mother, which displayed hemolytic anemia and thrombocytopenia. In the second family, the patients displayed typical features of ODDD, and Sanger sequencing identified a novel homozygous c.604C>T (p.R202C) missense mutation, whereas the parents carried the mutation. Together, these findings suggest that homozygous mutation in GJA1 induces a more severe ODDD phenotype, though interfamilial phenotype variability was observed, whereas compound heterozygous mutations in GJA1 cause a mild phenotype.

Congenital Lower Extremity Anomaly Pathology and Reconstruction: A Review of the Literature

SUMMARY

With the advent of the subspecialty of orthoplastic surgery, there has been a greater involvement of plastic surgeons in limb reconstruction, congenital anomalies, and salvage procedures. Understanding embryology helps plastic surgeons better understand how to reconstruct lower extremity congenital defects and how development of the lower limb affects what can be done to reconstruct the adult lower limb. There is significant discussion in the literature regarding embryology and development of craniofacial structures and the upper extremity; however, the development of the lower limb remains largely unexplored. This review aims to elucidate the embryologic development of the lower limb, congenital anomalies that may present to the plastic surgeon, and reconstructive options.

Burden of congenital and hereditary anomalies in the war-affected territory at Pakistan-Afghanistan border

Background

Pashtun populations of Pakistan are the victim of long-lasting military combats, rendering 1.9 million inhabitants internally displaced. Studies highlighting congenital and hereditary anomalies in these populations are deficient.

Objectives

To elucidate the spectrum anomalies in the north-western war-affected territories of Pakistan.

Methods

A cross-sectional study was carried out from 2017 to 2019 and individuals or families with anomalies were ascertained through convenience and cluster random sampling. Phenotypic and pedigree data and information on bio-demographic variables were collected. Descriptive statistics were applied.

Results

A total of 361 independent individuals or families with anomalies were recruited. The anomalies were grouped into 8 major and 72 minor entities. Among major categories, neurological disorders had the highest representation (n = 100; proportion: 0.277; 95% CI: 0.231-0.323), followed by sensorineural defects (n = 70; prop.: 0.194), limb defects (n = 60; prop.: 0.166), visual impairments (n = 55; prop.: 0.152), and musculoskeletal defects (n = 37; prop.: 0.102). Among the neurological disorders, intellectual disability had the highest occurrence (58%), whereas talipes and limb amputations were the most prominent in limb defects (22% and 20%, respectively). The anomalies had sporadic and isolated presentations most often (76% each), while parental consanguinity was observed in 34% of index cases.

Conclusions

The high incidence of neurological, sensorineural, and limb defects, the preponderance of sporadic cases, and low level of parental consanguinity may indicate a potentially high contribution of nongenetic factors in the etiology of anomalies. The majority of anomalies are the cause of severe disability.

Genetics of congenital anomalies of the hand

Congenital anomalies of the hand are malformations occurring during the development of the human limb, and present as isolated disorders or as a part of a syndrome. During the last years, molecular analysis techniques have offered increasing knowledge about the molecular basis of hand malformations. Disturbances in the signaling pathways during the development of the upper limb result in malformations of the upper extremity. At present, several genes have been identified as responsible for hand anomalies and other have been recognized as suspect genes related to them. Different and new high throughput methods have been introduced for the identification of the gene mutations. In the current editorial, we summarize concisely the current molecular status of isolated hand genetic disorders and the recent progress in molecular genetics, including the genes related to the disorder. This progress improves the knowledge of these disorders and has implications on genetic counselling and prenatal diagnosis.

Identification of a HOXD13 variant in a Mongolian family with incomplete penetrance syndactyly by exon sequencing

Background

Syndactyly (SD) refers to a deformity caused by the fusion and limb differentiation disorder of soft tissues and/or skeletons to varying extents between adjacent fingers (toes). The main features of this disease are phenotypic heterogeneity and genetic heterogeneity. In this study, we examined four generations of a Chinese Mongolian with different phenotypes of syndactylia and analysed and identified the pathogenic genetic variants of SD by exon sequencing.

Methods

The clinical phenotypes of patients were analysed, and the hands and feet were examined by X-ray. The pedigree was drawn, and the family data were analysed. Peripheral blood was collected from the family members, and genomic DNA was extracted. The candidate genes of SD were identified by exon sequencing, and the mutation sites of the captured candidate genes were amplified by PCR and verified by Sanger sequencing.

Results

The family has congenital syndactyly, which is an autosomal dominant disease. At present, this condition has been passed down for 4 generations and was identified in 9 patients, including 4 males and 5 females. Five patients, I₂, II₄, III₅, III_,7 and III₁₀, had unilateral syndactyly, and four patients, III₁₆, IV₃, IV₆ and IV₇, had bilateral finger syndactyly. All of their toes were unaffected. The proband and the other patients in this family had a c.917G > A (p.R306Q) mutation, which is located at position 917 of the second exon of the HOXD13 gene. This mutation results in a change in the amino acid at position 306, in which arginine is changed to glutamine. This mutation cosegregates in unaffected individuals and affected patients in this family. Moreover, 201 Mongolian genome databases and a thousand human genome databases were referenced to further confirm that the pathogenic genetic variant that causes syndactyly in this family is found in HOXD13.

Conclusion

This study found that the mutation site of the pathogenic gene in this family was HOXD13, c.917G > A (p.R306Q). The phenotype of the family member III₁₂ was normal, but this member was also a carrier of the pathogenic genetic variant. This indicates that the disease of this family has incomplete penetrance characteristics. Our results further enrich the expression profile of the HOXD13 gene.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01360-3.

Separation of congenital embryonic syndactylies in children: dorsal or volar flap? About a comparative retrospective series

Congenital syndactylies account for 1 to 2 out of 2000 birth defects. Although several types of syndactylies exist, we only studied embryonic syndactylies. The goal of our study was to compare 2 types of coverage flap for the reconstruction of the finger web spaces: a volar flap described by Blauth and a dorsal flap described by Gilbert. Between 1993 and 2015, children affected by simple and complex syndactylies (partial or complete) were treated in 2 french pediatric hospitals and were selected for our analytic, comparative, retrospective review. The 2 hospitals used different surgical techniques: one used a volar flap described by Blauth and the other a dorsal flap described by Gilbert. The children were followed up to look for signs according to the stages of the Classification of Withey and to evaluate a global result according to the score of Withey. Our secondary criteria of judgement were the aspect of the surgical scar according to the VSS (Vancouver Scar Scale) and the satisfaction of the parents and children. The age of the children, need for a surgical revision and time of last follow- up were also studied. We found statistically significant differences between group I (volar flap) and group II (dorsal flap) in favor of the volar flap: higher scores of Withey (even when the number of commissures was increasing) and better VSS (regardless of the number of web spaces treated). There was no statistically significant difference between the 2 groups in terms of age, follow-up, or rate of surgical revision. All in all, the volar flap presented less sequelae in terms of scar retraction. Regardless of the flap used, the cosmetic results of the full-thickness skin graft used impacted the result both on the receiving site (dyschromia, hairiness) and the donor site.

Single-stage Congenital Polysyndactyly Release: Outcomes and Long-term Followup

The current surgical strategy for syndactyly is multistage operations in which every other web is released, leaving adjacent webs unoperated for the next stage to avoid a presumed possible digital vascular compromise. In this series, we present our experience with single-stage multiple syndactylies release. A total of 7 patients, including 2 patients with bilateral hand involvement, were included. Dorsal and volar triangular flaps were created for commissure reconstruction, and zigzag manner volar and dorsal incisions were made to release the webbed fingers. Sterile thermoplastic splints were molded directly over the skin grafts without any dressing or tie-over. Following the surgical operation, minimal flexion contracture was seen in three patients that needed future correction procedures. Cosmesis and functional outcome were acceptable. This study shows that the release of all webs in 1 setting can be accomplished by no vascular compromise, and there is no need for a preoperative vascular imaging study.

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.

Case report: Bilateral simple Syndactyly in a toddler with maternal exposure to cabergoline

Cabergoline is routinely prescribed in the management of prolactin excreting adenomas and is associated with low risk of congenital malformations and teratogenicity. Here, we reported the case of a bilateral simple syndactyly in a toddler with maternal exposure to cabergoline during the pregnancy. This association has not been previously described before.

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.

Readability and Quality Assessment of Online Materials for Syndactyly Release

Syndactyly is one of the most common congenital hand malformations, involving an abnormal fusion of digits and with treatment varying according to its complexity. The internet has become a primary source of information for both families and patients with congenital hand anomalies. The purpose of this study was to evaluate both the readability and quality of available web content for syndactyly, using validated instruments.

Preoperative MRI Evaluation of Hand Vessels in Children With Congenital Syndactyly Malformation by a Contrast-Enhanced Three-Dimensional Water-Selective Cartilage Scan

BACKGROUND

It is crucial to preoperatively assess the arteries of the hands in congenital syndactyly malformation (CSM) patients because this information can affect the therapeutic outcome and prognosis.

OBJECTIVE

To investigate the value of a contrast-enhanced three-dimensional water-selective cartilage scan for the preoperative evaluation of CSM in children.

MATERIALS AND METHODS

Contrast-enhanced three-dimensional water-selective cartilage scan 3.0 T magnetic resonance imaging (MRI) performed in 16 clinically diagnosed CSM patients with 17 affected hands. The arteries of the hands were displayed with a focus on the bifurcation position of the common palmar digital arteries (CPDAs) and the maturity of the proper palmar digital arteries (PPDAs). The MRI results were interpreted by consensus between two experienced pediatric radiologists with 10 years of MRI experience each. The MRI findings were compared with the operation results.

RESULTS

Of 51 CPDAs in the 17 affected hands, MRI showed that 30 had an abnormal bifurcation position and 20 had a normal position, and of the 102 PPDAs, 14 were shown to have an abnormal maturity and 85 a normal state, which were confirmed by surgery. The accuracy, sensitivity and specificity for determining the bifurcation position of the CPDAs based on MR maximum intensity projection reconstructed images were 98.04% (50/51), 96.77% (30/31) and 100% (20/20), respectively. The maturity of the PPDAs was judged by MR maximum intensity projection reconstructed images with an accuracy, sensitivity and specificity of 97.06% (99/102), 82.35% (14/17) and 100% (85/85), respectively.

CONCLUSION

Contrast-enhanced three-dimensional water-selective cartilage scan has excellent performance in displaying the bifurcation position of the CPDAs and the maturity of the PPDAs and is of high value for the preoperative evaluation of CSM in children.

Syndactyly Release in the Hand: Surgical Technique

SUMMARY

Syndactyly is one of the most common congenital differences treated by hand surgeons. Although dozens of techniques for syndactyly release have been described, a reliable method is based on a dorsal rectangular flap for commissure construction and a combination of interdigitating zigzag flaps and skin grafts for digital coverage. In this article, the authors present a detailed description of syndactyly release emphasizing principles integral to successful outcomes.

Surgical treatment in child's congenital toe syndactyly: Risk factor of recurrence, complication and poor clinical outcomes

INTRODUCTION

Surgical treatment of toe syndactyly remains controversial. The strong demand from parents for a cosmetic release is increasing in our societies. But is it worth it? The objective was to assess medium-long term outcomes and to identify the risk factors of recurrence, complication and poor clinical outcomes.

METHODS

Sixty-eight toe syndactylies (38 patients) undergoing surgery between 2008 and 2017 with a follow-up higher than two years were included consecutively and retrospectively. Four children (four syndactylies) were lost to follow-up and excluded. The mean age of the first surgery was 3.9 years old (0.8-16.7) and cohort mean follow-up was 6.9 years (2.8-11.2). In all patients, web release with a commissural dorsal flap was performed and associated a cutaneous resurfacing (spontaneous epithelialization, full-thickness skin graft taken from the popliteal crease, or a hyaluronic acid ester matrix).

RESULTS

Eighteen syndactylies (28.1%) in 14 patients recurred and one syndactyly required revision surgery. An age of surgery above two years was the only risk factor for recurrence found in univariate (OD = 0.27[0.08;0.85];p = 0.02) and multivariate studies (IC 95% = 0.05-0.68;p = 0.02). Seven complications (11.7%) in seven syndactylies (6 patients) were reported with six keloids (9.4%) and one scar retraction (1.6%). Each complication underwent an additional procedure. African ethnicity (N = 15) represents a risk factor (N = 4/15; OD = 0.12[0.009;0.97];p = 0.02) for keloids formation. Withey's average score is 4.9 (1-11), mean OxAFQ-C score was 52/60 (30-60), 67% would repeat the surgery and 69% felt satisfied at last follow-up. The simple syndactyly would appear less satisfied than complex or complicated (p = 0.02).

CONCLUSIONS

Surgical treatment of child's congenital syndactyly involves a risk of recurrence (28%) and potential complications (11,7%). Performed surgical procedure over two years old increase the risk of recurrence. African ethnicity is a risk factor in scarring complication. Only half of simple syndactylies are satisfied and prone to repeat the surgery.

From Mendel laws to whole genetic association study to decipher the swine mulefoot phenotype

The swine mulefoot (SM) is a rare condition characterized by a non-cloven hoof due to the partial or total fusion of the phalanges. No comprehensive study has been conducted to identify associated markers with this phenotype until now. We aimed to characterize the association between SNP and the mulefoot phenotype using a Genome-Wide Association Study (GWAS). An experimental population was produced using a half-sib mating where the male had the mulefoot phenotype and the females (n = 6) had cloven hoofs. The cross resulted in 27 (47%) animals with the mulefoot characteristic and 30 (53%) normal animals, indicating the possible dominant gene action. Animals were further genotyped using the Illumina PorcineSNP50k BeadChip, and SNPs were tested for associations. Twenty-nine SNPs located on the SSC15, SSC4, and SSCX were associated with the mulefoot phenotype (p-value <5 × 10^-5). Six markers were found in the intronic regions of VWC2L, CATIP, PDK3, PCYT1B, and POLA1 genes. The marker rs81277626, on SSC15:116,886,110 bp, is located in the Von Willebrand Factor C Domain (VWC2L), a possible functional candidate gene. The VWC2L is part of a biological process involved with the bone morphogenetic protein (BMP) signaling pathway, previously associated with syndactyly in other species. In conclusion, the identified markers suggest the involvement of the VWC2L gene in the SM phenotype in this population.

Long-read whole genome sequencing reveals HOXD13 alterations in synpolydactyly

Synpolydactyly 1, also called syndactyly type II (SDTY2), is a genetic limb malformation characterized by polydactyly with syndactyly involving the webbing of the third and fourth fingers, and the fourth and fifth toes. It is caused by heterozygous alterations in HOXD13 with incomplete penetrance and phenotypic variability. In our study, a five-generation family with an SPD phenotype was enrolled in our Rare Disease Genomics Protocol. A comprehensive examination of three generations using Illumina short-read whole-genome sequencing (WGS) did not identify any causative variants. Subsequent WGS using Pacific Biosciences (PacBio) long-read HiFi Circular Consensus Sequencing (CCS) revealed a heterozygous 27-bp duplication in the polyalanine tract of HOXD13. Sanger sequencing of all available family members confirmed that the variant segregates with affected individuals. Reanalysis of an unrelated family with a similar SPD phenotype uncovered a 21-bp (7-alanine) duplication in the same region of HOXD13. Although ExpansionHunter identified these events in most individuals in a retrospective analysis, low sequence coverage due to high GC content in the HOXD13 polyalanine tract makes detection of these events challenging. Our findings highlight the value of long-read WGS in elucidating the molecular etiology of congenital limb malformation disorders.

Complex radial polydactyly in a Chinese family: inclusion of triphalangism, triplication, and syndactyly

Background

Few studies have investigated families in which multiple individuals over three or more generations are affected by radial polydactyly and syndactyly. This report describes an extremely rare family in which nine individuals across six generations were affected by complex radial polydactyly.

Methods

We investigated a six-generation pedigree with radial polydactyly including triplication, triphalangism, hypoplasia, and symphalangism. There was a total of 34 individuals (including their spouses) in the family and 11 individuals had polydactyly. The average age of the patients ranged from 7 months to 96 years. The characteristic feature of the malformation in these patients was described. Two patients underwent surgical resection for radial supernumerary thumbs. The Bilhout-Cloquet technique and On-top-plasty technique were used to reconstruct the nail and the joints.

Results

The patients in this family presented with thumb duplication and triphalangism in both hands, including a variety of deformities, such as triplication, triphalangism, hypoplasia, and symphalangism. Syndactyly and ulnar polydactyly were also frequently observed. Two patients who underwent surgical treatment showed good hand and thumb function at the 8- and 2-year post-operative follow-up, respectively.

Conclusions

The present study reported various mixed phenotypes including triplication, triphalangism, hypoplasia, and symphalangism within the same family which may represent a rare type of polydactyly. Surgical resection of extra digits to achieve mobility of the thumb is the main treatment option for radial polydactyly. Given the ulnar thumb is better developed, the radial thumb is typically resected in patients with radial polydactyly. These reconstructive principles are fit for this Chinese family as well.

Basal epidermis collective migration and local Sonic hedgehog signaling promote skeletal branching morphogenesis in zebrafish fins

Teleost fish fins, like all vertebrate limbs, comprise a series of bones laid out in characteristic pattern. Each fin's distal bony rays typically branch to elaborate skeletal networks providing form and function. Zebrafish caudal fin regeneration studies suggest basal epidermal-expressed Sonic hedgehog (Shh) promotes ray branching by partitioning pools of adjacent pre-osteoblasts. This Shh role is distinct from its well-studied Zone of Polarizing Activity role establishing paired limb positional information. Therefore, we investigated if and how Shh signaling similarly functions during developmental ray branching of both paired and unpaired fins while resolving cellular dynamics of branching by live imaging. We found shha is expressed uniquely by basal epidermal cells overlying pre-osteoblast pools at the distal aspect of outgrowing juvenile fins. Lateral splitting of each shha-expressing epidermal domain followed by the pre-osteoblast pools precedes overt ray branching. We use ptch2:Kaede fish and Kaede photoconversion to identify short stretches of shha+basal epidermis and juxtaposed pre-osteoblasts as the Shh/Smoothened (Smo) active zone. Basal epidermal distal collective movements continuously replenish each shha+domain with individual cells transiently expressing and responding to Shh. In contrast, pre-osteoblasts maintain Shh/Smo activity until differentiating. The Smo inhibitor BMS-833923 prevents branching in all fins, paired and unpaired, with surprisingly minimal effects on caudal fin initial skeletal patterning, ray outgrowth or bone differentiation. Staggered BMS-833923 addition indicates Shh/Smo signaling acts throughout the branching process. We use live cell tracking to find Shh/Smo restrains the distal movement of basal epidermal cells by apparent 'tethering' to pre-osteoblasts. We propose short-range Shh/Smo signaling promotes these heterotypic associations to couple instructive basal epidermal collective movements to pre-osteoblast repositioning as a unique mode of branching morphogenesis.

A novel microdeletion upstream of HOXD13 in a Chinese family with synpolydactyly

Synpolydactyly (SPD) is a digital malformation with the typical clinical phenotype of the webbing of 3/4 fingers and/or 4/5 toes, and combined with polydactyly. In this study, we investigated a Chinese family with SPD and genetic analysis found that all of the affected individuals in the family carry a heterozygous 11,451 bp microdeletion at chr2:176933872-176945322 (GRCh37), which is located upstream of HOXD13 gene, the known disease gene for SPD1. All the affected individuals in the family carry the heterozygous deletion variant, and the variant co-segregated with SPD in the family. Thus, we speculate that the 11,451 bp microdeletion is the disease-causing variant in the family. To date, the microdeletion associating with SPD1 which we identified is the smallest deletion upstream of the HOXD13 gene and not altering the sequence of the HOXD13 gene.

Novel HOXD13 variants in syndactyly type 1b and type 1c, and a new spectrum of TP63-related disorders

Syndactyly is the most common limb defect depicting the bony and/or cutaneous fusion of digits. Syndactyly can be of various types depending on the digits involved in the fusion. To date, eight syndactyly-associated genes have been reported, of which HOXD13 and GJA1 have been explored in a few syndactyly but most of them have unknown underlying genetics. In the present study HOXD13, GJA1 and TP63 genes have been screened by resequencing in 24 unrelated sporadic cases with various syndactyly. The screening revealed two pathogenic HOXD13 variants, NM_000523:c.500 A > G [p.(Y167C)], and NM_000523:c.961 A > C [p.(T321P)] in syndactyly type 1b and type 1c, respectively. This is the first report to identify HOXD13 pathogenic variant in syndactyly type 1b and third report in syndactyly type 1c pathogenesis. Furthermore, this study also reports a TP63 pathogenic variant, NM_003722:c.953 G > A [p.(R318H)] in Ectrodactyly and Cleft lip and palate (ECLP). In conclusion, the current study expands the clinical spectrum of HOXD13 and TP63-related disorders.

Congenital limb defects in a married female population of the Rahim Yar Khan District in Pakistan

Background

Congenital limb defects (CLD) have a range of phenotypes and can be a substantial cause of disability. The prevalence of CLD in the adult population of Pakistan is not well described.

Objectives

To investigate the prevalence of CLD and their associated factors in a married female population of the Rahim Yar Khan (RYK) District in Pakistan.

Methods

A cross-sectional population-based study was conducted in 4 tehsils of RYK District, and married women and girls from 22 different localities were enrolled by convenience sampling in public places and through door-to-door visits. Data regarding limb phenotype and demographic variables were obtained from participants.

Results

We enrolled 2,204 married women and girls. We found 11 participants with CLD suggesting a prevalence of 4.99/1,000 (proportion: 0.005; 95% confidence interval [CI] <0.001-0.01). Polydactyly was the most frequent (n = 5; prevalence: 2.27/1,000), followed by others in the following sequence: brachydactyly (n = 4; prevalence: 1.81/1,000), camptodactyly (n = 1; prevalence: 0.45/1,000), and oligodactyly (n = 1; prevalence: 0.45/1,000). The odds of occurrence of CLD were higher in individuals originating from Khanpur tehsil (odds ratio [OR] 2.05; 95% CI 0.37-11.27), speaking languages other than Punjabi and Saraiki (OR 2.35; 95% CI 0.24-22.80), belonging to Araien caste (OR 2.35; 95% CI: 0.24-22.80), of a nuclear family (OR 3.35; 95% CI 0.79-16.97), or having parental consanguinity (OR 1.87; 95% CI 0.49-7.06).

Conclusion

Preliminary estimate of CLD prevalence in the married female sample population in RYK appears high compared with estimates from birth defects registries in other countries.

Novel Use of Pennig External Fixation for the Treatment of Pediatric Syndactyly

Syndactyly is one of the most common congenital limb malformations, second only to polydactyly. Syndactyly is treated with surgical intervention. During separation, free skin grafting or skin flap transplantation is required to allow for adequate skin closure. We introduce a novel application method of the Pennig external fixation device for the management of pediatric syndactyly without skin grafting. The Pennig minifixator was used in syndactyly to expand the web space soft tissue in order to allow a Z-plasty to be performed in a second operation. All patients had developed sufficient skin tissue from the external fixation. No infection, cutaneous necrosis or nonunion was noted in any of the patients. All patients had a satisfactory outcome in terms of final appearance and digit function. On the basis of the principle of strain-stress, use of the Penning external minifixator allows development of sufficient tissue in the web space for a second phase of reconstruction in syndactyly. The need for skin grafting and risk of blood vessel damage were avoided in this study, and, the incidence of skin necrosis and scar formation was reduced. Both the patients' families and our research members expressed high satisfaction with the postoperative function and appearance. Overall, application of the Pennig external fixation frame in our novel method is effective for the management of syndactyly and should be studied further. Level of Evidence: Level IV, case series.

The Operative Incidence of Syndactyly in Northern Ireland. A 10-Year Review

BACKGROUND

Syndactyly is a common congenital condition that can present sporadically or in relation to an underlying genetic condition. Little contemporary published data exists detailing specific rates of presentation and surgical intervention, especially in Western European population. This is the first published review of operative intervention rates for the condition over time in Northern Ireland.

METHODS

A ten-year retrospective review of electronic operative records from January 2007 - October 2017 was carried out within Northern Ireland's regional tertiary centre Royal Belfast Hospital for Sick Children (RBHSC). All congenital hand surgery in the country was performed here during the period reviewed, by a single surgeon. Patient age at surgical intervention, their sex, digits involved and clinical grade of syndactyly was recorded.

RESULTS

One hundred and twenty four cases were returned following the review. On individual analysis 22 cases were excluded as they were not primary congenital syndactyly. The remaining 102 cases were all Caucasian. Six cases were toe syndactyly while 96 cases involved the upper limb digits. The group consisted of 70 males and 32 female infants. Age range at time of surgical intervention was 8 months to 14 years with a median age of 26 months. For clinical grade of upper limb syndactyly; 35 cases in the data set were classed as simple incomplete, 34 cases as simple complete, 17 as complex and 5 cases as complicated syndactyly. The remaining 5 cases lacked clear documentation. The most common site of syndactyly was between the ring and middle finger (40/102). Annual frequency of operative intervention has trended upwards in the period studied.

CONCLUSION

This case review adds epidemiological data on the operative incidence of syndactyly cases in Northern Ireland - a relatively isolated genetic population. Overall rates of incidence have increased over the past 10 years. It remains unclear if this is due to new environmental influences on the developing population or increased referral for surgical intervention over time.Levels of evidence - IV (Case Series).

Syndactyly

Here we present an interesting case of simple syndactyly and provide a narrative review of its incidence, associations and management.

Lethal Cenani Lenz syndrome in two consecutive pregnancies: Further extension of phenotype from Maldives

Cenani Lenz syndrome is a rare autosomal recessive disorder associated with variable degree of limb malformations, dysmorphism, and renal agenesis. It is caused due to pathogenic variants in the LRP4 gene, which plays an important role in limb and renal development. Mutations in the APC gene have also been occasionally associated with CLS. The phenotypic spectrum ranges from mild to very severe perinatal lethal type depending on the type of variant. We report a pathogenic variant, c.2710 del T (p.Trp904GlyfsTer5) in theLRP4 gene, in a fetus with lethal Cenani Lenz syndrome with antenatal presentation of tetraphocomelia and symmetrical involvement of hands and feet.

Alazami syndrome: Phenotypic expansion and clinical resemblance to Smith-Lemli-Opitz syndrome

Biallelic mutations in the LARP7 gene have been recently shown to cause Alazami syndrome, a rare condition characterized by short stature, intellectual disability, and peculiar facial dysmorphisms. To date, only 24 cases have been reported. Here, we describe two brothers initially suspected to have Smith-Lemli-Opitz syndrome, in whom clinical exome sequencing detected a novel homozygous truncating variant in LARP7. These cases expand the phenotypic spectrum of Alazami syndrome to include toes syndactyly and adaptive behavior, and confirm the power of "genotype first" approach in patients with syndromic presentations overlapping distinct rare conditions.

Cell death in the developing vertebrate limb: A locally regulated mechanism contributing to musculoskeletal tissue morphogenesis and differentiation

Our aim is to critically review current knowledge of the function and regulation of cell death in the developing limb. We provide a detailed, but short, overview of the areas of cell death observed in the developing limb, establishing their function in morphogenesis and structural development of limb tissues. We will examine the functions of this process in the formation and growth of the limb primordia, formation of cartilaginous skeleton, formation of synovial joints, and establishment of muscle bellies, tendons, and entheses. We will analyze the plasticity of the cell death program by focusing on the developmental potential of progenitors prior to death. Considering the prolonged plasticity of progenitors to escape from the death process, we will discuss a new biological perspective that explains cell death: this process, rather than secondary to a specific genetic program, is a consequence of the tissue building strategy employed by the embryo based on the formation of scaffolds that disintegrate once their associated neighboring structures differentiate.

We examine the functions of cell death in the formation and growth of the limb primordia.

We analyze the plasticity of the cell death program by focusing on the developmental potential of progenitors prior to death.

Considering the prolonged plasticity of progenitors to escape from the death process and the absence of defined genetic program in their regulation we propose that cell death is a consequence of the tissue building strategy employed by the embryo regulated by epigenetic factors .

National Patterns in Surgical Management of Syndactyly: A Review of 956 Cases

Purpose: Being one of the most common congenital hand malformations, syndactyly is repaired by orthopedic, plastic, and fellowship-trained general surgeons. Limited multi-institutional outcomes analyses regarding incidence, timing, and type of repair exist. Methods: All syndactyly cases performed over a 5-year period from 2012-2016 were isolated from the National Surgical Quality Improvement Program Pediatric database. Patient demographics, surgical factors, perioperative outcomes, and risk factors were analyzed using χ², Fisher exact, and t-test analysis. Results: A total of 956 patients who underwent syndactyly repair were identified. Most cases were simple syndactyly with nearly even case distribution among plastic and orthopedic surgeons. Most patients were men and Caucasian. Mean age at the time of surgery was 2.6 years. Most cases were performed as outpatient surgery. Patients of plastic surgeons had significantly more airway abnormalities and shorter operative times. Patients with complex syndactyly had significantly more ventilator dependence, tracheostomy, and comorbidities when compared with those with simple syndactyly. Cases with complex syndactyly also had longer operative times and a higher rate of superficial surgical site infections. Conclusions: Syndactyly repair is a safe procedure with few major or minor reconstructive complications regardless of the surgical specialty or syndactyly type. Patients with complex syndactyly have significantly more preoperative comorbidities with comparable outcomes. orthopedic surgeons have significantly longer operative times than plastic surgeons, likely due to caring for increased number of patients with complex syndactyly.

Alcohol consumption before pregnancy causes detrimental fetal development and maternal metabolic disorders

Alcohol consumption before or during pregnancy poses serious health risks to the fetus; however, the underlying mechanisms involved remain obscure. Here, we investigated whether ethanol consumption before pregnancy affects maternal or fetal health and whether pharmacological inhibition of CYP2E1, a major ethanol oxidation enzyme, by 4-methylpyrazole (4-MP) has therapeutic effects. We found that ethanol consumption (5%) 2 weeks before pregnancy resulted in a decrease in the number of viable fetuses and abnormal fetal development, and these effects were accompanied by impaired maternal glucose homeostasis and hepatic steatosis during pregnancy. Neonates of ethanol-fed mice had postnatal macrosomia and significantly decreased growth rates during the lactation period. However, treatment with 4-MP, a CYP2E1 inhibitor, markedly ameliorated the reduction in insulin action and glucose disposal responsiveness in the livers of ethanol-fed mice. Blockage of CYP2E1 significantly reduced the alteration in hepatic lipid deposition, fatty acid oxidation, mitochondrial energy status, and macrophage infiltration observed in ethanol-fed mice. Finally, there was a positive correlation between postnatal macrosomia or growth retardation and increased inflammatory responses. Collectively, our study suggests that even moderate ethanol intake may be detrimental to fetal development and may cause growth retardation through maternal metabolic disorders.

A Review of the Phenotype of Synpolydactyly Type 1 in Homozygous Patients: Defining the Relatively Long and Medially Deviated Big Toe with/without Cupping of the Forefoot as a Pathognomonic Feature in the Phenotype

Synpolydactyly type 1 (SPD1, OMIM 186000) is inherited as autosomal dominant and is caused by HOXD13 mutations. The condition is rare and is known for its phenotypic heterogeneity. In the homozygous state, the phenotype is generally more severe and is characterized by three main features: a more severe degree of syndactyly, a more severe degree of brachydactyly, and the frequent loss of the normal tubular shape of the metacarpals/metatarsals. Due to the phenotypic heterogeneity and the phenotypic overlap with other types of syndactyly, no pathognomonic feature has been described for the homozygous phenotype of SPD1. In the current communication, the author reviews the literature on the phenotypes of SPD1 in homozygous patients. The review documents that not all homozygous patients show a severe hand phenotype. The review also defines the “relatively long and medially deviated big toe with/without cupping of the forefoot” as a pathognomonic feature in the phenotype. Illustration of this feature is done through a demonstrative clinical report in a multigeneration family with SPD1 and HOXD13 polyalanine repeat expansion. Finally, the pathogenesis of the clinical features is reviewed.