Book a test
On this page
⚠ Educational content only Not medical or genetic advice. Speak with a healthcare provider or genetic counsellor before acting on anything here.
Immunology

Hereditary alpha-tryptasaemia

This condition is thought to affect a significant portion of the population and may lead to a range of symptoms, including reactions to insect stings, certain foods, or medications. It involves an inherited increase in specific tryptase genes.

Autosomal dominant Immunology
~5% population
Prevalence
Population estimate
50%
Inheritance
Autosomal dominant - chance of passing to each child

Overview

Hereditary alpha-tryptasaemia is a genetic characteristic that can result in persistently higher-than-average levels of alpha-tryptase in the bloodstream. Tryptase is an enzyme primarily released by mast cells, which are part of the immune system and play a role in allergic reactions and inflammation. While tryptase levels can temporarily rise during an acute allergic reaction, individuals with hereditary alpha-tryptasaemia often have elevated levels even when not experiencing an allergic event [PMID:33621422]. This baseline elevation is a key feature of the condition.

Symptoms & clinical features

Individuals with hereditary alpha-tryptasaemia may experience a variety of symptoms, though the severity and presentation can differ greatly between people. Common symptoms reported include increased susceptibility to severe reactions from insect stings, certain foods, or medications. Other manifestations can include skin issues such as flushing, itching, or hives, and gastrointestinal symptoms like abdominal pain, diarrhoea, or bloating. Some individuals also report neurological symptoms, such as light-headedness or dizziness. many people with elevated alpha-tryptase levels may not experience significant symptoms [PMID:27874288].

Video: Genetics 101

Affected organs

Hereditary alpha-tryptasaemia primarily affects systems involving mast cells and allergic responses. This includes the skin, where flushing, itching, and hives can occur. The gastrointestinal tract is often impacted, leading to symptoms such as abdominal discomfort, nausea, and changes in bowel habits. The cardiovascular system can also be involved, with reported symptoms like low blood pressure or light-headedness, particularly during severe reactions. The respiratory system may experience symptoms such as wheezing or shortness of breath in some individuals.

Immune cells
Immune cells
Immune system dysfunction
Cellular impact
Cellular impact
Mechanism at cellular level

Risks & severity

The severity of hereditary alpha-tryptasaemia symptoms can vary widely. Some individuals may have no noticeable symptoms despite elevated tryptase levels, while others may experience significant impacts on their quality of life. Research suggests a link between hereditary alpha-tryptasaemia and an increased risk of severe reactions, such as anaphylaxis, especially in response to insect stings or certain medications [PMID:33621422]. The exact lifetime risks associated with this condition are still being studied, and not everyone with the genetic predisposition will develop severe symptoms. The condition is present from birth, but symptoms may emerge at any age.

Genetic causes

Hereditary alpha-tryptasaemia is linked to an increased number of copies of the alpha-tryptase gene, specifically the TPSAB1 gene. Most people typically have two copies of this gene, but individuals with hereditary alpha-tryptasaemia usually have three or more functional copies [PMID:27874288]. These extra gene copies lead to the overproduction of alpha-tryptase, resulting in the elevated baseline levels observed in the blood. The exact mechanisms by which these increased gene copies cause the diverse range of symptoms are still an active area of research, but it is thought to relate to mast cell activation and mediator release.

Inheritance pattern

Hereditary alpha-tryptasaemia is inherited in an autosomal dominant pattern. This means that a person only needs to inherit one copy of the altered gene (in this case, having extra copies of the TPSAB1 gene) from one parent to have the predisposition. If one parent has hereditary alpha-tryptasaemia, there is a 50% chance with each pregnancy that their child will also inherit the genetic characteristic. The condition affects males and females equally. Family members may have varying levels of tryptase or different symptoms, even with the same genetic predisposition.

♀ Affected parent 1 altered copy ♂ Unaffected parent 2 typical copies Affected Unaffected Unaffected Affected Affected Carrier Unaffected Circles = females · Squares = males

Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.

Diagnosis & testing

Diagnosis of hereditary alpha-tryptasaemia typically begins with the observation of persistently elevated baseline serum tryptase levels, in the absence of other obvious causes for this elevation. Genetic testing can then confirm the presence of increased copies of the alpha-tryptase gene (TPSAB1). Referral to clinical genetics services in the UK can be made by a GP or specialist if hereditary alpha-tryptasaemia is suspected. Genetic testing for this condition may be performed under an NHS R-code, facilitating genomic analysis to determine gene copy number. A genetic counsellor can help interpret test results and discuss implications for the individual and their family.

Management & lifestyle

Management of hereditary alpha-tryptasaemia focuses on addressing symptoms and reducing the risk of severe reactions. As individual experiences vary, a personalised management plan is developed in consultation with healthcare professionals. This may involve avoiding known triggers for allergic reactions where possible, and carrying emergency medication, such as adrenaline auto-injectors, for individuals at risk of anaphylaxis. Symptomatic treatment for gastrointestinal issues or skin manifestations may also be recommended. Regular monitoring by an immunologist or allergist is often advised to track symptoms and tryptase levels. Engagement with an NHS clinical genetics service can provide further guidance on the genetic aspects and inheritance.

UK care pathway

Within the UK, if hereditary alpha-tryptasaemia is suspected, individuals are typically referred to specialist services such as immunology or allergy clinics. If genetic testing is deemed appropriate, this can be facilitated through the NHS Genomic Medicine Service (GMS), often after a referral to a regional clinical genetics service. Genetic counsellors play a crucial role in explaining the genetic basis of the condition, inheritance patterns, and potential implications for family members. Testing for gene copy number variations can be accessed via specific PanelApp R-codes where available, guiding the diagnostic pathway.

Frequently asked questions

What is alpha-tryptase?

Alpha-tryptase is an enzyme released primarily by mast cells, which are immune cells involved in allergic reactions and inflammation. In hereditary alpha-tryptasaemia, there are often higher baseline levels of this enzyme in the blood due to an increased number of certain genes.

Is hereditary alpha-tryptasaemia a rare condition?

No, it is not considered rare. Research suggests that hereditary alpha-tryptasaemia may affect approximately 5% of the general population, making it more common than many other genetic conditions. However, not everyone with the genetic predisposition experiences noticeable symptoms.

Can hereditary alpha-tryptasaemia cause severe allergic reactions?

Some individuals with hereditary alpha-tryptasaemia have an increased risk of severe reactions, including anaphylaxis, especially in response to insect stings, certain foods, or medications. It is important to discuss your specific risks with a healthcare professional.

How is hereditary alpha-tryptasaemia diagnosed in the UK?

Diagnosis typically involves blood tests showing persistently high baseline tryptase levels, followed by genetic testing to confirm extra copies of the TPSAB1 gene. This process is usually managed through specialist clinics and NHS Genomic Medicine Services after a referral.

If I have hereditary alpha-tryptasaemia, will my children inherit it?

Hereditary alpha-tryptasaemia follows an autosomal dominant inheritance pattern. This means if you have the genetic predisposition, each of your children has a 50% chance of inheriting the same genetic characteristic.

References

  1. Pouessel G, Dribin TE, Tacquard C. Management of Refractory Anaphylaxis: An Overview of Current Guidelines. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology. 2024. PMID: 38866583
  2. Lang A. Hereditary alpha tryptasemia and food allergy. Frontiers in allergy. 2025. PMID: 40463362
  3. Caullery B, Bocquet A, Riou L. First demonstration of implication of hereditary alpha-tryptasaemia in vasospastic angina: a case report. European heart journal. Case reports. 2025. PMID: 40144693
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor.