Hemoglobinopathy prevention in primary care: a reflection of underdetection and difficulties with accessibility of medical care, a quantitative study

As in most Northern European countries, the prevalence of hemoglobinopathies in The Netherlands is increasing due to migration. Although hemoglobinopathies are severe chronic diseases with few treatment options, timely detection of carriers allows at-risk couples to make informed reproductive choices such as pre-implantation diagnosis, prenatal diagnosis or termination of affected pregnancies. Using a quantitative design, we evaluated the prevalence of hemoglobinopathies in The Hague region, The Netherlands. Patient and carrier registries from hospital, laboratory and general practitioners allowed this quantitative analysis. The highest prevalence of hemoglobinopathies was seen in immigrant neighborhoods, and a large gap was noted between estimated carrier prevalence and the actual registration of carriers in electronic patient records. Carrier prevalence was estimated to be 13,704; however, the ELAN database contains only 1542 cases with ICPC codes for sickle cell disease or thalassemia. Although more research is needed to define the requirements of the healthcare system to address this challenge, this study clearly shows the gap between estimated carrier prevalence and registration and thereby the pressing need for action.Genetics of disease, diagnosis and treatmen

Breakpoint characterization of a rare alpha(0)-thalassemia deletion using targeted locus amplification on genomic DNA

Introduction The high-sequence homology of the alpha-globin-gene cluster is responsible for microhomology-mediated recombination events during meiosis, resulting in a high density of deletion breakpoints within a 10 kb region. Commonly used deletion detection methods, such as multiplex ligation-dependent probe amplification (MLPA) and Southern blot, cannot exactly define the breakpoints. This typically requires long-range PCR, which is not always successful. Targeted locus amplification (TLA) is a targeted enrichment method that can be used to sequence up to 70 kb of neighboring DNA sequences without prior knowledge about the target site. Methods Genomic DNA (gDNA) TLA is a technique that folds isolated DNA, ensuring that adjacent loci are in a close spatial proximity. Subsequent digestion and religation form DNA circles that are amplified using fragment-specific inverse primers, creating a library that is suitable for Illumina sequencing. Results Here, we describe the characterization of a rare 16 771 bp deletion, utilizing gDNA TLA with a single inverse PCR primer set on one end of the breakpoint. Primers for breakpoint PCR were designed to confirm the deletion breakpoints and were consequently used to characterize the same deletion in 10 additional carriers sharing comparable hematologic data and similar MLPA results. Conclusions The gDNA TLA technology was successfully used to identify deletion breakpoints within the alpha-globin cluster. The deletion was described only once in an earlier study as the --(gb), but as it was not registered correctly in the available databases, it was not initially recognized as such.Genetics of disease, diagnosis and treatmen

Cyanosis, hemolysis, decreased HbA1c and abnormal co-oximetry in a patient with hemoglobin M Saskatoon [HBB:c.190C > T p.His64Tyr]

We describe a first Dutch case of Hb M Saskatoon (HBB:c.190C > T p.His64Tyr) in a 47-year-old female Dutch patient who presented with cyanosis, hemolysis, and abnormal co-oximetry. A mean corpuscular volume (MCV) of 105 fL caused by reticulocytosis (160 x 10(9)/L) and low red blood cell count (3.6 x 10(12)/L) suggested an increased erythrocyte turnover. An HPLC glyco-globin analysis revealed a decreased HbA1c fraction of 12.3 mmol/mmol, HbA0 of 93.3% and an additional unidentified fraction at 1.2 min. DNA sequencing revealed a missense mutation in the HBB gene, (HBB:c.190C > T p.His64Tyr), known as Hb M Saskatoon, a variant which has been previously identified as an unstable hemoglobin variant leading to methemoglobinemia and anemia. In this report, we describe the clinical and remarkable laboratory aspects of our patient with Hb M Saskatoon, and the consequences for treatment and drug use.Genetics of disease, diagnosis and treatmen

A remarkable case of HbH disease illustrates the relative contributions of the alpha-globin enhancers to gene expression

Genetics of disease, diagnosis and treatmen

Adapting the ACMG/AMP variant classification framework: a perspective from the ClinGen Hemoglobinopathy Variant Curation Expert Panel

Accurate and consistent interpretation of sequence variants is integral to the delivery of safe and reliable diagnostic genetic services. To standardize the interpretation process, in 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published a joint guideline based on a set of shared standards for the classification of variants in Mendelian diseases. The generality of these standards and their subjective interpretation between laboratories has prompted efforts to reduce discordance of variant classifications, with a focus on the expert specification of the ACMG/AMP guidelines for individual genes or diseases. Herein, we describe our experience as a ClinGen Variant Curation Expert Panel to adapt the ACMG/AMP criteria for the classification of variants in three globin genes (HBB, HBA2, and HBA1) related to recessively inherited hemoglobinopathies, including five evidence categories, as use cases demonstrating the process of specification and the underlying rationale.Genetics of disease, diagnosis and treatmen

Usefulness of NGS for diagnosis of dominant beta-thalassemia and unstable hemoglobinopathies in five clinical cases

Unstable hemoglobinopathies (UHs) are rare anemia disorders (RADs) characterized by abnormal hemoglobin (Hb) variants with decreased stability. UHs are therefore easily precipitating, causing hemolysis and, in some cases, leading to dominant beta-thalassemia (dBTHAL). The clinical picture of UHs is highly heterogeneous, inheritance pattern is dominant, instead of recessive as in more prevalent major Hb syndromes, and may occur de novo. Most cases of UHs are not detected by conventional testing, therefore diagnosis requires a high index of suspicion of the treating physician. Here, we highlight the importance of next generation sequencing (NGS) methodologies for the diagnosis of patients with dBTHAL and other less severe UH variants. We present five unrelated clinical cases referred with chronic hemolytic anemia, three of them with severe blood transfusion dependent anemia. Targeted NGS analysis was performed in three cases while whole exome sequencing (WES) analysis was performed in two cases. Five different UH variants were identified correlating with patients' clinical manifestations. Four variants were related to the beta-globin gene (Hb Bristol-Alesha, Hb Debrousse, Hb Zunyi, and the novel Hb Mokum) meanwhile one case was caused by a mutation in the alpha-globin gene leading to Hb Evans. Inclusion of alpha and beta-globin genes in routine NGS approaches for RADs has to be considered to improve diagnosis' efficiency of RAD due to UHs. Reducing misdiagnoses and underdiagnoses of UH variants, especially of the severe forms leading to dBTHAL would also facilitate the early start of intensive or curative treatments for these patients.Genetics of disease, diagnosis and treatmen

Summary of joint European Hematology Association (EHA) and EuroBloodNet recommendations on diagnosis and treatment of methemoglobinemia

Genetics of disease, diagnosis and treatmen

Recommendations for diagnosis and treatment of methemoglobinemia

Methemoglobinemia is a rare disorder associated with oxidization of divalent ferro-iron of hemoglobin (Hb) to ferri-iron of methemoglobin (MetHb). Methemoglobinemia can result from either inherited or acquired processes. Acquired forms are the most common, mainly due to the exposure to substances that cause oxidation of the Hb both directly or indirectly. Inherited forms are due either to autosomal recessive variants in the CYB5R3 gene or to autosomal dominant variants in the globin genes, collectively known as HbM disease. Our recommendations are based on a systematic literature search. A series of questions regarding the key signs and symptoms, the methods for diagnosis, the clinical management in neonatal/childhood/adulthood period, and the therapeutic approach of methemoglobinemia were formulated and the relative recommendations were produced. An agreement was obtained using a Delphi-like approach and the experts panel reached a final consensus >75% of agreement for all the questions.Genetics of disease, diagnosis and treatmen

Effect of pH and soybean cultivars on the quantitative analyses of soybean rhizobia populations

Microbial Biotechnolog

Diagnosis of haemoglobinopathies: New scientific advances

Genetics of disease, diagnosis and treatmen