What causes low white blood cell count
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Causes of Low White Blood Cell Count
Genetic Factors and Ethnic Variations in White Blood Cell Count
Genetic factors play a significant role in determining white blood cell (WBC) counts, with notable variations observed among different ethnic groups. Research has shown that African Americans generally have lower WBC counts compared to European Americans. This difference has been linked to a specific genetic locus on chromosome 1q, which affects the expression of the Duffy blood group antigen. Individuals with the common West African allele at this locus tend to have lower WBC counts compared to those with the common European alleles 15. This genetic variant explains approximately 20% of the population variation in WBC counts among these groups .
Polygenic Predisposition to Lower White Blood Cell Counts
A polygenic predisposition, involving multiple genetic variations, also contributes to lower WBC counts. This predisposition is not necessarily linked to disease but can influence clinical outcomes. For instance, individuals with a genetic predisposition to lower WBC counts are at an increased risk of leukopenia when treated with chemotherapeutic or immunosuppressant drugs. They are also more likely to discontinue treatments like azathioprine due to adverse effects . This suggests that genetic predisposition can impact clinical care and treatment responses.
Genetic Loci and Immune-Mediated Diseases
Large-scale genetic studies have identified several loci associated with WBC traits, many of which are also linked to immune-mediated diseases. These loci include genes involved in the differentiation and function of various WBC lineages, such as myeloid and lymphoid cells. For example, genes like CD69, CD33, and ASXL1 play roles in hematopoiesis and immune responses. Variants in these genes can lead to lower WBC counts and are often pleiotropically associated with autoimmune diseases . This highlights the complex genetic architecture that regulates WBC counts and its overlap with immune system function.
Aging and White Blood Cell Count
Aging is another factor that influences WBC counts. As individuals age, there is a decline in the number and quality of lymphoid progenitor cells, which are crucial for immune responses. This decline is part of the natural aging process and is thought to be driven by inherent, programmed processes within stem and progenitor cells. Studies have shown that WBC counts, particularly lymphocyte counts, peak in early childhood and gradually decline with age. This decline is more pronounced in individuals aged 75 and older, making WBC count a potentially useful clinical indicator of survival in elderly populations .
Conclusion
Low white blood cell count can be attributed to a combination of genetic factors, polygenic predispositions, and aging. Genetic variations, particularly those affecting the Duffy blood group antigen, play a significant role in ethnic differences in WBC counts. Polygenic factors can influence clinical outcomes and treatment responses, while aging leads to a natural decline in WBC counts. Understanding these factors is crucial for developing personalized medical approaches and improving clinical care for individuals with low WBC counts.
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