Prenatal diagnosis and preimplantation genetic diagnosis: novel technologies and state of the art of PGD in different regions of the world

The Clinical Genetics of Hemophilia B (Factor IX Deficiency)

Hemophilia B (HB) is a bleeding disorder caused by deficiency of or defect in blood coagulation factor IX (FIX) inherited in an X-linked manner. It results from one of over 1000 known pathogenic variants in the FIX gene, F9; missense and frameshift changes predominate. Although primarily males are affected with HB, heterozygous females may have excessive bleeding due to random or non-random X chromosome inactivation; in addition, homozygous, compound heterozygous, and hemizygous females have been reported. Somatic and germinal mosaicism for F9 variants has been observed. Development of antibodies to FIX treatment products (inhibitors) is rare and related to the type of causative variant present. Treatment is with products produced by recombinant DNA technology, and gene therapy is in clinical trials. Genetic counseling with up-to-date information is warranted for heterozygotes, potential heterozygotes, and men and women affected with HB.

European principles of care for women and girls with inherited bleeding disorders

INTRODUCTION

Despite increasing awareness of issues faced by women and girls with inherited BDs (WGBD), standards of care are lacking, with disparities in diagnosis and treatment for WGBD across Europe. We aimed to develop practical principles of care (PoC) to promote standardization of care for WGBD within European Haemophilia Treatment and Comprehensive Care Centres (HTC/CCCs).

METHODS

The co-creation process, supported by the European Association for Haemophilia and Allied Disorders, consisted of four multidisciplinary meetings with health care providers (HCPs) experienced in WGBD care, and European Haemophilia Consortium representatives, combined with broad patient and HCP consultations in the European haemophilia community. Relevant medical societies outside Europe were contacted for confirmation.

RESULTS

We developed ten PoC for WGBD, stressing the importance and benefits of a centralized, multidisciplinary, comprehensive, family-centred approach to support and manage WGBD during all life stages. These PoC emphasise the right to equitable access and quality of care for all people with BDs, irrespective of gender. Multiple medical societies outside Europe also confirmed their support for endorsement.

CONCLUSIONS

Ten PoC for WGBD evolved from an iterative process among stakeholders, supported by relevant medical societies worldwide. These PoC can serve as a benchmark for diagnosis and comprehensive multidisciplinary management of WGBD, and improve awareness of their unique challenges. They offer a framework to guide HTC/CCCs in providing equitable care for all WGBD, both in their own services and in other healthcare settings. Implementation of these principles aims to positively impact the health, wellbeing and quality of life for WGBD.

Occurrence rates of haemophilia among males in the United States based on surveillance conducted in specialized haemophilia treatment centres

INTRODUCTION

Estimates of the size and characteristics of the US haemophilia population are needed for healthcare planning and resource needs assessment. A network of comprehensive haemophilia treatment centres (HTCs) located throughout the United States receives federal support for diagnosis and management of haemophilia and other rare bleeding disorders.

AIM

Estimate the incidence and prevalence of haemophilia among US males using the HTC network.

METHODS

During the period 2012-2018, de-identified surveillance data were collected on all males who visited an HTC that included year of birth, gender, race, Hispanic ethnicity, residence zip code, haemophilia type and severity. Data from all patients were used to calculate period prevalence by haemophilia type, severity and state of residence. Data from a subset of patients born 1995-2014 were used to estimate incidence rates over the 20-year period.

RESULTS

During the period, 21 748 males with haemophilia visited the HTCs resulting in an age-adjusted prevalence of 15.7 cases per 100 000 males (12 for haemophilia A and 3.7 for haemophilia B). Prevalence was higher among whites (15.1) than blacks (12.4) or Hispanics of either race (12.4). State-specific prevalence varied from 1.6 to 23.3 cases per 100 000. Based on 9587 males born during the index period, the average haemophilia incidence was 1 case per 4334 live male births.

CONCLUSION

Based on these data, we estimate that there are between 29 761 and 32 985 males with haemophilia living in the United States today, the majority of whom receive comprehensive care in specialized clinical centres.

Management of rare coagulation disorders in 2018

Rare bleeding disorders (RBDs) comprise inherited deficiencies of factors I (fibrinogen), II (prothrombin), V, VII, X, XI, and XIII as well as combined factor V + VIII and vitamin K-dependent factors. They represent 3-5% of all congenital bleeding disorders and are usually transmitted as autosomal recessive traits. These disorders often manifest during childhood and have varied clinical presentations from mucocutaneous bleeding to life-threatening symptoms such as central nervous system and gastrointestinal bleeding. Bleeding manifestations generally vary within the same RBD and may also vary from 1 RBD to the other. Laboratory diagnosis is based on coagulation screening tests and specific factor assays, with molecular techniques providing diagnostic accuracy and enabling prenatal counseling. The approach to treatment of bleeding episodes and invasive procedures needs to be individualized and depends on the severity, frequency and procedure-related risk of bleeding. The first line of treatment of RBDs is replacement of the deficient factor, using specific plasma-derived or recombinant products and using fresh frozen plasma or cryoprecipitate when specific products are not available or in resource-limited countries. Prophylaxis may be considered in individuals with recurrent serious bleeding and especially after life-threatening bleeding episodes. Novel no-replacement strategies promoting hemostasis by through different mechanisms need to be studied in RBDs as alternative therapeutic options.

Case Study: Cystic Fibrosis in the Newborn

Cystic fibrosis (CF) is considered one of the most commonly occurring fatal genetic disorders. This disorder is associated with pancreatic insufficiency and pulmonary complications. However, at birth the initial complications are associated with bowel obstruction. Cystic fibrosis management warrants an interdisciplinary team because this disorder affects various organ systems. Effective management of the newborn with CF assists in improving the child's overall prognosis. Family support is critical throughout the prenatal and postnatal periods. The case presented reviews a child born with suspected CF and the clinical course within the NICU.

Embryo cell allocation patterns are not altered by biopsy but can be linked with further development

It has been suggested that first embryo cleavage can be related with the embryonic-abembryonic axis at blastocyst stage in mice. Thus, cells of the 2-cell embryo might be already biased to form the inner cell mass or trophectoderm. This study was conducted to observe the possible effects of embryo biopsy on cell allocation patterns during embryo preimplantation in two different mouse strains and the effects of these patterns on further development. First, one blastomere of the 2-cell embryo was injected with a lipophilic tracer and cell allocation patterns were observed at blastocyst stage. Blastocysts were classified into orthogonal, deviant or random pattern. For the first experiment, embryos were biopsied at 8-cell stage and total cell counts (TCC) were annotated. Furthermore, non-biopsied blastocysts were transferred into foster mothers. Then, pups and their organs were weighed two weeks after birth. Random pattern was significantly recurrent (≈60%), against orthogonal (<22%) and deviant (<22%) patterns among groups. These patterns were not affected by biopsy procedure. However, TCC on deviant embryos were reduced after biopsy. Moreover, no differences were found between patterns for implantation rates, litter size, live offspring and organ weights (lungs, liver, pancreas and spleen). However, deviant pups presented heavier hearts and orthogonal pups presented lighter kidneys among the group. In conclusion, these results suggest that single blastomere removal does not disturb cell allocation patterns during pre-implantation. Nonetheless, the results suggest that embryos following different cell allocation patterns present different coping mechanisms against in vitro manipulations and further development might be altered.

Noninvasive prenatal diagnosis for X-linked disease by maternal plasma sequencing in a family of Hemophilia B

OBJECTIVE

To apply a Hidden Markov Model to test Hemophilia B in a fetus by maternal plasma sequencing only employing proband and maternal haplotypes.

CASE REPORT

A family at risk for Hemophilia B was recruited in this study. We performed genetic diagnosis on the proband using our targeted capture system (containing F9 gene coding region, highly heterozygous SNPs and a 13-kb chromosome Y specific region), and revealed a causative F9 gene mutation (c.190T>C, p.Cys64Arg). Maternal plasma cell-free DNA obtained at 8 weeks of gestation was targeted-captured and sequenced using the customized system. The fetus inherited the F9 (c.190T>C, p.Cys64Arg) mutation according to the Hidden Markov Model. The mother continued the pregnancy.

CONCLUSIONS

This study is the first report of a haplotype-based approach in NIPD of Hemophilia B. With further evaluation, this method might be useful for NIPD of Hemophilia B and for other X-linked single-gene disorders.

The past and future of haemophilia: diagnosis, treatments, and its complications

Haemophilia A and B are hereditary haemorrhagic disorders characterised by deficiency or dysfunction of coagulation protein factors VIII and IX, respectively. Recurrent joint and muscle bleeds lead to severe and progressive musculoskeletal damage. Existing treatment relies on replacement therapy with clotting factors, either at the time of bleeding (ie, on demand) or as part of a prophylactic schedule. The major complication of such therapy is the development of neutralising antibodies (ie, inhibitors), which is most frequent in haemophilia A. Treatment might improve considerably with the availability of new modified drugs, which might overcome existing prophylaxis limitations by reducing dosing frequency and thereby rendering therapy less distressing for the patient. Subcutaneous administration of some new therapies would also simplify prophylaxis in children with poor venous access. Gene therapy has the potential for a definitive cure, and important results have been obtained in haemophilia B. Despite improvements in haemophilia care, the availability of clotting factor concentrates for all affected individuals worldwide remains the biggest challenge.

Oncofertility in adolescent and young adult hereditary cancer: Considerations for genetics professionals

Adolescents and young adults (AYA) with a cancer diagnosis or those at risk for cancer due to hereditary cancer syndromes may benefit from genetic counseling and testing not only to manage personal risk but also to address reproductive concerns, especially fertility. The opportunity for genetic counselors to provide important risk information is relevant to both the newly diagnosed as well as to unaffected carriers and survivors. However, genetic counselors may need additional training in reproductive options related to AYA cancer to provide this valuable counsel. This commentary uses hereditary breast and ovarian cancer syndrome as a model to highlight important considerations when discussing preimplanatation genetic diagnosis and prenatal diagnosis, particularly in the context of expanded testing for hereditary cancer risk including multigene panels or whole exome or whole genome sequencing. Other hereditary cancers are also addressed; however, less is known about the psychosocial and fertility concerns in these AYA populations. Additionally, we provide an overview of the concept of “oncofertility” - the linkage between cancer care and reproductive medicine that aims to expand the reproductive opportunities of cancer patients - and offer support for the expansion of guidelines to include genetic counselors in AYA cancer patients’ treatment planning related to reproductive health and fertility.

The Challenges and Opportunities Associated with Sickle Cell Disease Prevention, Education, and Management

Sickle cell disease (SCD) is a hereditary blood disorder affecting the shape of the red blood cells that block blood vessels leading to organ damage and frequent erratic painful episodes. SCD is a global public health issue affecting millions of people throughout the world. This article explores (a) what SCD is; (b) the physical and psychosocial impacts of the disease;

Hemophilia B: molecular pathogenesis and mutation analysis

Hemophilia B is an X-chromosome-linked inherited bleeding disorder primarily affecting males, but those carrier females with reduced factor IX activity (FIX:C) levels may also experience some bleeding. Genetic analysis has been undertaken for hemophilia B since the mid-1980s, through linkage analysis to track inheritance of an affected allele, and to enable determination of the familial mutation. Mutation analysis using PCR and Sanger sequencing along with dosage analysis for detection of large deletions/duplications enables mutation detection in > 97% of patients with hemophilia B. The risk of the development of inhibitory antibodies, which are reported in ~ 2% of patients with hemophilia B, can be predicted, especially in patients with large deletions, and these individuals are also at risk of anaphylaxis, and nephrotic syndrome if they receive immune tolerance induction. Inhibitors also occur in patients with nonsense mutations, occasionally in patients with small insertions/deletions or splice mutations, and rarely in patients with missense mutations (p.Gln237Lys and p.Gln241His). Hemophilia B results from several different mechanisms, and those associated with hemophilia B Leyden, ribosome readthrough of nonsense mutations and apparently 'silent' changes that do not alter amino acid coding are explored. Large databases of genetic variants in healthy individuals and patients with a range of disorders, including hemophilia B, are yielding useful information on sequence variant frequency to help establish possible variant pathogenicity, and a growing range of algorithms are available to help predict pathogenicity for previously unreported variants.

Current status of preimplantation genetic diagnosis in Japan

This is a retrospective study aimingto clarify the current status of preimplantation genetic diagnosis (PGD) in Japan. Our data were collected from 12 facilities between September 2004 and September 2012, and entered into a database. A majority of PGD in Japan was performed for balanced structural chromosomal abnormalities in couples with recurrent miscarriage. PGD for monogenic diseases was performed only in two facilities. The average maternal age was 38 years for monogenic diseases and 40 years for chromosomal abnormalities. Overall there have been671 cycles to oocyte retrieval reported. Of these cycles, 85% (572 cycles)were for chromosomal abnormalities, and 15% (99 cycles) for monogenic diseases. Diagnosis rates in the current study were 70.8% for monogenic diseases and 94.0% for chromosomal abnormalities. Rates of embryo transfer of PGD were 62.7% for monogenic diseases and 25.5% for chromosomal abnormalities. Clinical pregnancy rates per embryo transfer were 12.0% for monogenic diseases and 35.6% for chromosomal abnormalities. Our study is the first PGD report from all facilities which had the approval of the ethics committee of the Japanese Society of Obstetrics and Gynecology. We have built a basis for gathering continuous PGD data in Japan.