Hereditary alpha tryptasemia (HαT) is an inherited genetic trait in which you carry extra copies of a gene called TPSAB1, causing higher-than-normal levels of a protein called alpha-tryptase. This leads to elevated tryptase in your blood and can be linked to allergy-type and mast cell symptoms. It affects an estimated 4–6% of Western populations studied to date — so you are not alone. Generally, the more extra copies of the gene you carry, the higher your tryptase level and the more likely you are to have symptoms.
What are mast cells and tryptase?
- Mast cells are immune cells that help your body fight infections and are involved in allergic reactions.
- When activated, they release chemicals including histamine and tryptase, which can cause flushing, hives, itching, swelling, and drops in blood pressure.
- In HαT, extra copies of the alpha-tryptase gene cause higher baseline tryptase in your blood — even when you feel perfectly well. This is not a cancer, and it is not an infection.
- Many people with HαT have few or no symptoms at all.
Possible symptoms
Skin
- Flushing or redness
- Itching or hives
- Angioedema (swelling)
Allergic
- More frequent reactions
- Severe anaphylaxis risk
- Insect sting sensitivity
Gastrointestinal
- Abdominal pain or cramping
- Diarrhea or bloating
- IBS-like symptoms
Cardiovascular
- Light-headedness
- Fast heart rate
- Low blood pressure
Neurologic / Neuropsychiatric
- Fatigue or exhaustion
- Sleep disturbances
- Memory problems / "brain fog"
- Depression or anxiety
- Headache or chronic pain
Autonomic / Connective Tissue
- POTS (rapid heart rate on standing)
- Joint hypermobility (hEDS-like)
- Dizziness or fainting
Other Associations
- Thyroid disorders (e.g., Hashimoto's)
- Scoliosis or back pain
- Autoimmune conditions (emerging research)
How is HαT diagnosed?
- Blood tryptase test: Drawn when you feel well, at least 24 hours after any allergic reaction. A level above 8 ng/mL may suggest HαT; a level above 10 ng/mL is more strongly suggestive. A level below 8 ng/mL makes HαT much less likely.
- Genetic test: If your tryptase is elevated and your history fits, your clinician may order a TPSAB1 copy-number test to confirm extra copies of the alpha-tryptase gene.
- Additional evaluation: Your care team may also check for related conditions like mast cell activation syndrome (MCAS) or systemic mastocytosis if indicated.
Is it inherited?
- Yes — HαT is autosomal dominant, meaning inheriting the extra gene copies from just one parent is enough to have the trait.
- Each of your children has a 50% chance of inheriting it.
- Family members with unexplained high tryptase, severe allergies, or anaphylaxis may be candidates for testing — speak with your healthcare provider.
Treatment & day-to-day management
There is currently no medication that lowers tryptase levels directly. Treatment focuses on managing your symptoms and avoiding your personal triggers.
💊 Medications (individualized)
- H1 antihistamines — for itching, hives, flushing, and some GI symptoms
- H2 blockers — for reflux and mast cell mediator symptoms
- Cromolyn sodium — mast cell stabilizer for significant GI complaints
- Corticosteroids — short courses for specific situations, under supervision
- Epinephrine autoinjector — if you have a history of anaphylaxis
- Omalizumab — biologic used off-label in difficult cases at specialty centers
🌿 Lifestyle & trigger management
- Identify and avoid personal triggers — foods, medications (especially NSAIDs), insect stings, temperature changes, strong smells, or stress
- Keep a symptom diary to track flares and possible exposures
- Stay well hydrated and avoid overheating
- Discuss work or exercise accommodations with your doctor if needed
- Consider a medical alert bracelet if you are at risk for anaphylaxis
🚨 Urgent
When to call 911 or go to the ER
- Trouble breathing, throat or tongue swelling, or wheezing
- Dizziness, fainting, or signs of very low blood pressure
- Widespread hives plus any difficulty breathing or a sense of impending doom
⚡ If you have been prescribed an epinephrine autoinjector (EpiPen), use it at the first sign of a severe reaction — then call 911 or go to the emergency room immediately.
Key takeaways
1
HαT is a common inherited trait affecting an estimated 4–6% of Western populations studied — not a cancer and not an infection. Most research to date has been in predominantly Caucasian groups; prevalence in other populations is still being studied.
2
Many people are minimally symptomatic, but some experience significant allergy-type, GI, pain, or autonomic symptoms.
3
There is no cure yet, but symptoms can often be well controlled with medications and trigger avoidance guided by your specialist.
4
Ask questions. Your allergy/immunology or mast cell specialist is your best resource for personalizing your care plan.