Role of Genetic Factors in the Pathogenesis of Radial Deficiencies in Humans

Investigating the role connective tissue fibroblasts play in the altered muscle anatomy associated with the limb abnormality, Radial Dysplasia

Radial dysplasia (RD) is a congenital upper limb birth defect that presents with changes to the upper limb anatomy, including a shortened or absent radius, bowed ulna, thumb malformations, a radially deviated hand and a range of muscle and tendon malformations, including absent or abnormally shaped muscle bundles. Current treatments to address wrist instability caused by a shortened or absent radius frequently require an initial soft tissue distraction intervention followed by a wrist stabilisation procedure. Following these surgical interventions, however, recurrence of the wrist deviation remains a common, long-term problem following treatment. The impact of the abnormal soft connective tissue (muscle and tendon) anatomy on the clinical presentation of RD and the complications following surgery are not understood. To address this, we have examined the muscle, fascia and the fascial irregular connective tissue (ICT) fibroblasts found within soft connective tissues, from RD patients. We show that ICT fibroblasts isolated from RD patients are functionally abnormal when compared to the same cells isolated from control patients and secrete a relatively disordered extracellular matrix (ECM). Furthermore, we show that ICT fibroblast dysfunction is a unifying feature found in RD patients, even when the RD clinical presentation is caused by distinct genetic syndromes.

Cardiomyopathy associated 5 (CMYA5) implicated as a genetic risk factor for radial hemimelia in Siamese cats

OBJECTIVES

The present study aimed to determine the inheritance pattern and genetic cause of congenital radial hemimelia (RH) in cats.

METHODS

Clinical and genetic analyses were conducted on a Siamese cat family (n = 18), including two siblings with RH. Radiographs were obtained for the affected kittens and echocardiograms of an affected kitten and sire. Whole genome sequencing was completed on the two cases and the parents. Genomic data were compared with the 99 Lives Cat Genome data set of 420 additional domestic cats with whole genome and whole exome sequencing data. Variants were considered as homozygous in the two cases of the siblings with RH and heterozygous in the parents. Candidate variants were genotyped by Sanger sequencing in the extended pedigree.

RESULTS

Radiographs of the female kitten revealed bilateral absence of the radii and bowing of the humeri, while the male kitten showed a dysplastic right radius. Echocardiography suggested the female kitten had restrictive cardiomyopathy with a positive left atrial-to-aortic root ratio (LA:Ao = 1.83 cm), whereas hypertrophic cardiomyopathy was more likely in the sire, showing diastolic dysfunction using tissue Doppler imaging (59.06 cm/s). Twenty-two DNA variants were unique and homozygous in the affected kittens and heterozygous in the parents. Seven variants clustered in one chromosomal region, including two frameshift variants in cardiomyopathy associated 5 (CMYA5) and five variants in junction mediating and regulatory protein, P53 cofactor (JMY ), including a missense and an in-frame deletion.

CONCLUSIONS AND RELEVANCE

The present study suggested an autosomal recessive mode of inheritance with variable expression for RH in the Siamese cat family. Candidate variants for the phenotype were identified, implicating their roles in bone development. These genes should be considered as potentially causal for other cats with RH. Siamese cat breeders should consider genetically testing their cats for these variants to prevent further dissemination of the suspected variants within the breed.

Thrombocytopenia Absent Radius (TAR)-Syndrome: From Current Genetics to Patient Self-Empowerment

Thrombocytopenia absent radius (TAR) syndrome is a rare form of hereditary thrombocytopenia associated with a bilateral radial aplasia. TAR syndrome is genetically defined by the combination of a microdeletion on chromosome 1 which includes the gene RBM8A, and a single nucleotide polymorphism (SNP) in the second RBM8A allele. While most patients with TAR syndrome harbor a SNP in either the 5' UTR region or in intron 1 of RBM8A, further SNPs associated with TAR syndrome are still being identified. Here, we report on the current understanding of the genetic basis, diagnosis, and therapy of TAR syndrome and discuss patient self-empowerment by enabling networking and exchange between affected individuals and families.

A Novel Germline Pathogenic Variant of RECQL4 Gene in an Iranian Pedigree with Familial Squamous Cell Carcinoma: A Brief Report

Squamous cell carcinoma (SCC) is the most common human solid tumor and the leading cause of cancer death. SCC of the breast is a very rare type of cancer that has not been well researched. Early identification of the genetic factors involved can lead to early diagnosis and targeted treatment. The present study was conducted in 2018 at Isfahan University of Medical Sciences (Isfahan, Iran). The proband was a 66-year-old woman with SCC of the breast and a positive family history of cancer. Blood DNA samples were used for whole-exome sequencing to identify germline pathogenic variants. Variant annotation and prioritization were done on variant call format files using bioinformatics software tools. The screened variants were confirmed using the Sanger sequencing method. Co-segregation analysis was performed on the blood DNA samples of the first- and second-degree relatives of the proband to assess the presence of the mutation. A novel germline pathogenic variant was identified in the RECQL4 gene of the family. RECQL4 is a known protein in DNA repair and replication. Considering its effect on other types of SCC, it may play an important role in SCC initiation and progression in the breast.

Thrombocytopenia With Absent Radii Syndrome With an Unusual Urological Pathology: A Case Report

Thrombocytopenia with absent radii (TAR) syndrome is a rare congenital syndrome that follows an autosomal recessive pattern of inheritance. TAR syndrome is characterized by thrombocytopenia and bilateral absence (aplasia) of the radii of the forearms. This syndrome can be associated with defects within the skeletal, cardiac, renal, or gastrointestinal systems. It is important for clinicians treating patients with TAR syndrome to be aware of the myriad of complications that may arise in the other organ systems in order to promptly diagnose and treat any associated anomalies. We present a case of an African American infant diagnosed with TAR syndrome who was also found to have grade 5 vesicoureteral reflux and moderate right hydronephrosis, as well as cow’s milk protein allergy.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from 2q11.1-q12.1 associated with fetal bilateral radial dysplasia

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from 2q11.1-q12.1 associated with fetal bilateral radial dysplasia.

CASE REPORT

A 27-year-old woman underwent amniocentesis at 18 weeks of gestation because of club hands on fetal ultrasound. The internal organs of the fetus were normal. Amniocentesis revealed a karyotype of 47,XY,+mar [13]/46,XY [11]. The parental karyotypes were normal. Simultaneous array comparative genomic hybridization (aCGH) analysis of the DNA extracted from uncultured amniocytes revealed the result of arr 2q11.1q12.1 (95,529,039-102,825,556) × 3.0 [GRCh37 (hg19)]. The pregnancy was terminated at 20 weeks of gestation, and a malformed fetus was delivered with isolated bilateral radial dysplasia. The cord blood had a karyotype of 47,XY,+mar[24]/46,XY[16]. Polymorphic DNA marker analysis of the DNAs extracted from umbilical cord and parental bloods excluded uniparental disomy for chromosome 2. Metaphase fluorescence in situ hybridization analysis confirmed an sSMC derived from chromosome 2q11.1-q12.1 in cultured amniocytes.

CONCLUSION

High-level mosaicism for an sSMC derived from chromosome 2q11.1-q12.1 can be associated with fetal abnormalities.

Phenotypic Diversity of 15q11.2 BP1-BP2 Deletion in Three Korean Families with Development Delay and/or Intellectual Disability: A Case Series and Literature Review

The 15q11.2 breakpoint (BP) 1–BP2 deletion syndrome is emerging as the most frequent pathogenic copy number variation in humans related to neurodevelopmental diseases, with changes in cognition, behavior, and brain morphology. Previous publications have reported that patients with 15q11.2 BP1–BP2 deletion showed intellectual disability (ID), speech impairment, developmental delay (DD), and/or behavioral problems. We describe three new cases, aged 3 or 6 years old and belonging to three unrelated Korean families, with a 350-kb 15q11.2 BP1–BP2 deletion of four highly conserved genes, namely, the TUBGCP5, CYFIP1, NIPA2, and NIPA1 genes. All of our cases presented with global DD and/or ID, and the severity ranged from mild to severe, but common facial dysmorphism and congenital malformations in previous reports were not characteristic. The 15q11.2 BP1–BP2 deletion was inherited from an unaffected parent in all cases. Our three cases, together with previous findings from the literature review, confirm some of the features earlier reported to be associated with 15q11.2 BP1–BP2 deletion and help to further delineate the phenotype associated with 15q11.2 deletion. Identification of more cases with 15q11.2 BP1–BP2 deletion will allow us to obtain a better understanding of the clinical phenotypes. Further explanation of the functions of the genes within the 15q11.2 BP1–BP2 region is required to resolve the pathogenic effects on neurodevelopment.

Prevalence and risk factors of radial ray deficiencies: A population-based case-control study

Radial ray deficiency is the most common congenital deficiency of the upper limb. The aim of our study was to investigate maternal risk factors for radial ray deficiencies. We conducted a nationwide population-based case-control study using national registers. All cases with a radial ray deficiency born between 1996 and 2008 were included in the study and compared with five controls without limb deficiency. In total, 115 (10 isolated, 18 with multiple congenital anomalies, and 87 syndromic) cases with radial ray deficiencies were identified and compared with 575 matched controls. The total prevalence in Finland was 1.22 per 10,000 births. No significant risk factors were observed for nonsyndromic cases. In the syndromic group, advanced maternal age (≥35 years) increased the risk of radial aplasia (aOR 2.45, 95% CI 1.37-4.36), and a similar association was observed with multiple pregnancy (aOR 2.97, 1.16-7.62) and male sex (aOR 1.96, 1.18-3.25). Valproic acid was also a risk factor (p = .002). In conclusion, novel associations in the syndromic group of advanced maternal age and multiple pregnancy and increased risk of radial ray deficiencies were observed. Also, early reports on increased risk of RRD associated with valproate and male sex were supported by our results.

Chromosome Instability in Fanconi Anemia: From Breaks to Phenotypic Consequences

Fanconi anemia (FA), a chromosomal instability syndrome, is caused by inherited pathogenic variants in any of 22 FANC genes, which cooperate in the FA/BRCA pathway. This pathway regulates the repair of DNA interstrand crosslinks (ICLs) through homologous recombination. In FA proper repair of ICLs is impaired and accumulation of toxic DNA double strand breaks occurs. To repair this type of DNA damage, FA cells activate alternative error-prone DNA repair pathways, which may lead to the formation of gross structural chromosome aberrations of which radial figures are the hallmark of FA, and their segregation during cell division are the origin of subsequent aberrations such as translocations, dicentrics and acentric fragments. The deficiency in DNA repair has pleiotropic consequences in the phenotype of patients with FA, including developmental alterations, bone marrow failure and an extreme risk to develop cancer. The mechanisms leading to the physical abnormalities during embryonic development have not been clearly elucidated, however FA has features of premature aging with chronic inflammation mediated by pro-inflammatory cytokines, which results in tissue attrition, selection of malignant clones and cancer onset. Moreover, chromosomal instability and cell death are not exclusive of the somatic compartment, they also affect germinal cells, as evidenced by the infertility observed in patients with FA.

Clinical and epidemiological features of heart-hand syndrome, an updated analysis in China

BACKGROUND

The purpose of this study was to prospectively recruit patients treated with limb malformation and to explore the prevalence and the clinical and epidemiological features of Heart-Hand Syndrome (HHS) in China.

METHODS

The consecutive patients treated for congenital upper limb malformation in Beijing Ji Shui Tan Hospital from October 1st, 2016 to October 1st, 2019 were prospectively recruited. We reviewed the patients' medical records and identified patients with abnormal electrocardiogram (ECG) and/or abnormal ultrasonic cardiogram as well as their basic demographic and clinical characteristics.

RESULTS

A total 1653 (1053 male and 600 female) patients with congenital upper extremity malformations were prospectively recruited. Among them, 200 (12.1%) had abnormal ultrasonic cardiogram (181patients, 10.9%) and/or abnormal ECG (19 patients, 1.1%). The commonest type of abnormal heart structure was atrial septal defect (69/181 38.1%), and the commonest abnormal ECG was wave patterns (7/19, 36.8%). HHS patients had a higher comorbidity rate (11%) than non-HHS patients (6.9%). Patients with HHS were classified into four groups by the types of congenital upper extremity malformations, among which the most common group was thumb type (121/200, 60.5%).

CONCLUSIONS

HHS occurred frequently among patients with congenital upper extremity malformation in China, particularly for those with multiple congenital malformations. The commonest type of hand malformations of HHS patients was thumb malformation.

Association of Radial Longitudinal Deficiency and Thumb Hypoplasia: An Update Using the CoULD Registry

BACKGROUND

Deficiency of the radial aspect of the forearm and hand is the most common congenital longitudinal deficiency of the upper limb. Radial longitudinal deficiency is associated with several named syndromes. The purpose of the present study was to explore patterns of radial longitudinal deficiency and thumb hypoplasia in syndromes and to examine the severity of these differences across various syndromes.

METHODS

Data were collected from the Congenital Upper Limb Differences (CoULD) registry. Congenital differences are classified in the registry with use of the Oberg-Manske-Tonkin (OMT) classification system. Diagnosis of a syndrome by a physician as noted in the CoULD registry was recorded. Thumb deficiency and radial deficiency were classified according to the modified versions of the Blauth criteria and the Bayne and Klug criteria, respectively.

RESULTS

We identified 259 patients with 383 affected limbs with radial deficiency. Eighty-three of these patients had a diagnosed syndrome. The severity of radial deficiency was correlated with the severity of thumb deficiency. The Kendall tau coefficient indicated significant correlation between radial severity and thumb severity (tau = 0.49 [95% confidence interval = 0.40 to 0.57]; p < 0.05). Subjects with a syndrome were twice as likely to have bilateral deficiency and 2.5 times more likely to have both radial and thumb deficiency compared with subjects without a syndrome. Subjects with VACTERL syndrome (vertebral defects, anal atresia, cardiac anomalies, tracheoesophageal fistula, renal anomalies, and limb defects) had patterns of thumb and radial deficiency similar to the general cohort, whereas subjects with Holt-Oram syndrome, TAR (thrombocytopenia absent radius) syndrome, and Fanconi anemia demonstrated varied presentations of thumb and radial deficiency.

CONCLUSIONS

The present study investigated the characteristics of patients with radial longitudinal deficiency and thumb hypoplasia. Our results support the findings of previous research correlating the severity of radial deficiency with the severity of thumb deficiency. Furthermore, we identified characteristic features of patients with radial longitudinal deficiency and associated syndromes.

Thrombocytopenia with absent radii (TAR) syndrome in a female neonate: a case report

Thrombocytopenia absent radius (TAR) syndrome is a rare congenital disorder that is consistently associated with skeletal abnormality and thrombocytopenic haemorrhage. This is a case of a neonate with bilateral absent radius and thrombocytopenia. The rarity of this case prompted this report.

On-Top Index Pollicization After a Partial Amputation of a Syndactylized Hypoplastic Thumb in a Patient With Townes-Brocks Syndrome

Townes-Brocks syndrome is a rare autosomal dominant syndrome characterized by multiple malformations, including thumb anomalies. Thumb hypoplasia poses a specific problem, where a deficient thumb creates a significant handicap in hand function. The treatment goal is enabling pinch and grip activity, and the preferred procedure for a severely hypoplastic thumb is index finger pollicization. We present a case of on-top index pollicization in a 10-year-old, after a partial amputation of a previously syndactylized hypoplastic thumb, with a well-formed first carpometacarpal joint. The decision to proceed with pollicization was made after considering second toe-to-hand transfer and a standard pollicization with an amputation of the thumb remnants. Six months after the procedure, the outcome was evaluated as "good" (19 points) with Percival's assessment method. The patient uses the operated hand in all activities of daily life and is doing well in school. This patient's diagnosis of Townes-Brocks syndrome was confirmed with genetic testing, which gives grounds and incentive to further investigate other possible related conditions, and provide genetic counselling and risk assessment. In reconstruction of complex thumb malformations, especially after previous multiple operations, an individually tailored reconstruction plan, sometimes involving modifications of standard reconstructive procedures, is paramount in achieving good results.