Decoding the Vel Blood Group System: Understanding, Diagnosing, and Utilizing Genetic Testing

Expert Reviewed By: ⁠Dr. Brandon Colby MD

The Vel blood group system is a rare and clinically significant blood group that can cause severe transfusion reactions in affected individuals. This article aims to provide an overview of the Vel blood group system, its genetic basis, and the role of genetic testing in understanding, diagnosing, and managing this condition.

A Brief Overview of the Vel Blood Group System

The Vel blood group system was first discovered in 1952 and is characterized by the presence or absence of the Vel antigen on the surface of red blood cells. Individuals who lack the Vel antigen are considered to have a “Vel-negative” blood type, which is a rare phenotype occurring in approximately 1 in 2,500 individuals of European descent. The clinical significance of the Vel blood group lies in its potential to cause severe transfusion reactions in Vel-negative individuals who receive Vel-positive blood.

Unraveling the Genetic Basis of the Vel Blood Group System

Recent advances in genomics have led to the identification of the gene responsible for the Vel blood group system. The Small Integral Membrane Protein 1 (SMIM1) gene has been identified as the locus of a novel erythrocyte membrane protein and the Vel blood group system (Storry et al., 2013). This gene encodes a tail-anchored transmembrane protein that readily forms homodimers (Westerberg et al., 2021). The absence of the Vel antigen on red blood cells is caused by a deletion in the SMIM1 gene, which results in a lack of protein expression (Christophersen, 2015).

Genetic Testing for the Vel Blood Group System

Genetic testing can play a crucial role in understanding, diagnosing, and managing the Vel blood group system. The following sections will discuss the various uses of genetic testing in the context of this blood group.

1. Identifying Vel-Negative Individuals

Genetic testing can be used to identify individuals who are Vel-negative by detecting the presence of the SMIM1 deletion. This information is particularly important for individuals who may require blood transfusions, as it can help to ensure that they receive compatible blood and avoid potentially life-threatening transfusion reactions.

2. Screening Blood Donors

Screening blood donors for the Vel blood group system can help to identify Vel-negative blood units, which are in high demand for transfusion to Vel-negative patients. By incorporating genetic testing into blood donor screening protocols, blood banks can more efficiently identify and allocate Vel-negative blood units, ultimately improving patient outcomes.

3. Assessing Risk of Hemolytic Disease of the Fetus and Newborn (HDFN)

Genetic testing for the Vel blood group system can also be useful in assessing the risk of hemolytic disease of the fetus and newborn (HDFN) in pregnant women. If a pregnant woman is Vel-negative and her partner is Vel-positive, there is a risk that their baby may inherit the Vel-positive blood type, potentially leading to HDFN. Genetic testing can help to identify at-risk couples and guide appropriate prenatal care and management.

4. Research and Understanding of the Vel Blood Group System

Finally, genetic testing plays a crucial role in advancing our understanding of the Vel blood group system and its clinical implications. By studying the genetic basis of this blood group, researchers can gain insights into the molecular mechanisms underlying transfusion reactions, develop more accurate diagnostic tools, and identify potential therapeutic targets for the prevention and treatment of transfusion-related complications.

Conclusion

The Vel blood group system is a rare and clinically significant blood group with the potential to cause severe transfusion reactions. Genetic testing for the SMIM1 gene has emerged as a valuable tool for understanding, diagnosing, and managing this condition, with applications ranging from identifying Vel-negative individuals and screening blood donors to assessing the risk of HDFN and advancing research in the field. As our understanding of the Vel blood group system continues to grow, genetic testing will undoubtedly play an increasingly important role in improving patient outcomes and advancing our knowledge of this complex blood group.

About The Expert Reviewer

Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of  and the author of ⁠⁠Outsmart Your Genes.

Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (⁠⁠ACMG), an Associate of the American College of Preventive Medicine (⁠⁠ACPM), and a member of the National Society of Genetic Counselors (⁠NSGC)