KIT D816V in People with Anaphylaxis and Mast Cell Activation Symptoms

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Welcome to the latest Allergy, Asthma & Immunology Innovations podcast. This episode is part of The Itch Review, where we highlight important research in allergy and immunology. In this episode, we look at the PROSPECTOR trial. This study asked: How often can doctors find the KIT D816V mutation with a regular blood test in people who had anaphylaxis or signs of mast cell reactions?

Our hosts, Payel Gupta, MD, and Kortney, are joined by Michael Blaiss, MD, to review the article, “Prevalence of KIT D816V in anaphylaxis or systemic mast cell activation,” published in the October 2025 issue of the Journal of Allergy and Clinical Immunology (JACI).

Clonal mast cell disease is often hard to diagnose. Symptoms are different person to person, tryptase levels can be normal, and bone marrow biopsies are not easy to get. This study shows how a KIT D816V blood test may help find clonal mast cell disease earlier in people who have had unexplained or very severe allergic reactions and may not receive a diagnosis otherwise.

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This podcast is for informational purposes only and does not substitute professional medical advice. Any mention of brands is also informational and not an endorsement. Always consult with your healthcare provider for any medical questions or concerns.

Thank you to Blueprint Medicines for sponsoring this podcast episode.

What is KIT D816V?

Mast cells are immune cells that help protect your body. But sometimes they can grow in the wrong way. When this happens, people may experience symptoms such as hives, flushing, stomach pain or severe allergic reactions called anaphylaxis.

Many people with clonal mast cell diseases, like systemic mastocytosis, have a mutation called KIT D816V. This mutation makes one mast cell create many extra copies of itself, leading to too many mast cells in the body. In the past, doctors usually needed a bone marrow biopsy to find this mutation. Today, newer blood tests can look for KIT D816V.

What we cover in this episode about the KIT D816V mutation

  • Understanding clonal mast cell disease.
  • What the KIT D816V mutation is and why testing matters.
  • Why it is important to test patients for hereditary alpha-tryptasemia (HaT)  and what tryptase levels mean for patients.  
  • What the PROSPECTOR trial found: How often the KIT D816V mutation showed up on a blood test, and what researchers learned about different groups of people who had anaphylaxis.
  • What it means for patients: How doctors use KIT testing, tryptase levels, HaT results, and symptoms together to decide who may need more testing for clonal mast cell disease.
An infographic summarizes a study on the prevalence of KIT D816V in anaphylaxis or systemic mast cell activation, highlighting objectives, methods, key findings, and primary and secondary endpoints, with color-coded sections and logos.
Click image to see full graphic or to download.

Timestamps for our podcast about testing for KIT D816V 

01:42 – What mast cell activation syndrome means

07:20 – What anaphylaxis is

10:19 – Understanding KIT D816V

13:27 – Tests used to look for mast cell disorders

19:14 – How the PROSPECTOR trial was designed

28:41 – What the PROSPECTOR trial found

39:13 – Strengths and limits of the study

41:37 – Doctor takeaways

Resources about mast cell disease

Other podcast episodes about mast cell diseases