What is it?

Hereditary Alpha tryptasemia (HaT) is a genetic trait caused by an extra copy of the TPSAB1 gene, which is responsible for an extra alpha -tryptase, leading to high tryptase levels in the blood. It is quite a common trait. Tryptase is a chemical produced by immune cells called mast cells during allergic reactions and is known to be higher in patients with HaT. It is not fully understood yet if having HaT is really linked or not to mast cell activation and anaphylaxis.

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Signs & symptoms

Symptoms may include increased frequency and severity of anaphylaxis events due to insect bites or idiopathic anaphylaxis, when the trigger is not found. Some other symptoms which may be linked are skin flushing, hives, itching, allergy to bee stings, chronic pain or skeletal abnormalities.


Many of the people with Hereditary Alpha tryptasemia are not diagnosed due to lack of symptoms. Diagnosis is done by genetic testing.


Most people with HaT will not require any treatment. Omalizumab and antihistamines may help for those who experience symptoms.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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