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JAK2 G571S Mutation: Benign Polymorphism Resolves Eosinophilia

Publication Title: Leukocytosis and a JAK2 mutation: The importance of expertise in somatic variant interpretation

Summary

Question
This study investigated whether a rare genetic variant in the JAK2 gene, called G571S, is associated with disease or if it is a harmless genetic variation. The researchers examined this question in the context of an 88-year-old patient who had chronic leukocytosis (high white blood cell count) with isolated eosinophilia (high levels of a specific type of white blood cell) and a history of Strongyloides infection (a parasitic infection).
Why it Matters
Interpreting rare genetic variants like JAK2 G571S is critical for accurate medical diagnoses and treatment decisions. Misinterpreting such variants as disease-causing could lead to unnecessary invasive procedures or treatments, while overlooking their benign nature could delay appropriate care. This study highlights the importance of combining genetic testing with clinical context to guide effective patient care. It also has broader implications for improving genetic diagnostics and understanding the role of genetic variations in disease.
Methods
The researchers conducted genetic testing on the patient’s blood and buccal (cheek) cells using next-generation sequencing (NGS), a method that allows for detailed analysis of multiple genes. They focused on identifying whether the JAK2 G571S variant was present in both types of cells, which would indicate a germline mutation (inherited genetic variation) rather than a somatic mutation (acquired in specific tissues).
Key Findings
The JAK2 G571S mutation was detected in both the patient’s blood and buccal cells at similar levels, confirming it as a germline mutation. No additional disease-causing mutations were found in a panel of 49 genes related to blood cancers. The patient’s eosinophilia resolved after restarting treatment for Strongyloides infection with ivermectin, suggesting that the genetic variant was not responsible for the condition.
Implications
These findings support the idea that the JAK2 G571S mutation is a benign polymorphism, meaning it is a harmless genetic variation rather than a cause of disease. The study emphasizes the importance of adjunct genetic testing and expert interpretation to avoid misdiagnosing such variants. Clinicians should carefully evaluate genetic results within the broader context of a patient’s medical history to guide treatment decisions effectively.
Next Steps
The authors recommend further studies on rare genetic variants like JAK2 G571S to better understand their clinical significance. They also suggest expanding the use of genetic testing in cases where initial results are inconclusive, to ensure accurate diagnoses and avoid unnecessary procedures.
Funding Information
This research was not supported by any external grants or funding organizations as stated in the publication. Yale University also provided funding and support for this research.

Full Citation

Puzo C, Hager K, Rose M, Wong E, Tormey C, Siddon A. Leukocytosis and a JAK2 mutation: The importance of expertise in somatic variant interpretation. Leukemia Research Reports 2026, 25: 100563. PMID: 41626141, PMCID: PMC12854866, DOI: 10.1016/j.lrr.2026.100563.
This AI-assisted summary has been reviewed and approved by at least one of the study's authors to ensure it accurately reflects the research.

Authors

  • Christian J. Puzo

    First Author
    School Building Streamline Icon: https://streamlinehq.comOther Institution

  • Alexa Siddon, MD

    Last Author
    Yale School of Medicine

    Professor of Laboratory Medicine

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Additional Yale School of Medicine Authors

Other Authors

  • Karl Hager;
  • Michal Rose;
  • Ellice Wong

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