Systemic mastocytosis (SM) and hereditary alpha-tryptasemia (HαT) have many overlapping features — and many people have both conditions. Here’s what that means for patients.
What is HαT?
HαT is a genetic disorder that leads to raised baseline serum tryptase levels. It is passed on in an autosomal dominant manner, meaning that if your parent has it, you have a 50% chance of inheriting the disorder.
Some of the more common symptoms of HαT include flushing, itching, abdominal pain, gastrointestinal dysfunction and allergies — symptoms that will sound very familiar to patients with SM.
There are no specific therapies for HαT. Treatments focus on relieving symptoms, and include antihistamines, corticosteroids, mast cell stabilizers and epinephrine — medications that will also be familiar to many patients with SM, especially those with milder forms of the disease.
Read more about SM treatment and care
Are HαT and systemic mastocytosis related?
SM and HαT share more than just overlapping symptoms.
Though HαT affects only 5%-8% of people in Western Europe and the U.S. (the areas where the disease is most common), research has found 18% of people with mastocytosis have the disorder.
They also share some of the same clinical findings. For example, basal serum tryptase levels are likely to be elevated in both SM and HαT.
HαT was only discovered in 2014, and science’s understanding of the disorder is in the early stages. Why patients with SM are more likely to have HαT and what links may exist between the two conditions isn’t fully understood.
What should people with SM know about HαT?
Allergic reactions to stringing insects like bees and wasps — called Hymenoptera venom allergy — are a concern for many with SM. Research suggests that people with HαT who are allergic to stinging insects are at risk of a much stronger reaction and anaphylaxis after a sting. Knowing you have both conditions can help your care team design a treatment plan that prioritizes lowering this risk.
Though SM and HαT share many of the same symptoms, existing research hasn’t found that having both conditions otherwise makes symptoms worse.
Could SM be misdiagnosed as HαT, or vice-versa?
In short: It’s very unlikely.
Because HαT and SM share many similar features, it may be challenging for doctors to arrive at an accurate diagnosis at first try. The symptoms of both these disorders are generally vague and non-specific, meaning that they can be attributed to a wide range of diseases. This is especially the case if you only have one or two symptoms.
But when symptoms persist, your doctor will eventually order testing to find their cause. Though SM and HαT have similar symptoms, their test results look very different. With results in hand, it should be clear to your doctors which of the two disorders you have.
Your doctor can confirm the diagnosis with genetic testing. HαT is caused by extra copies of the TPSAB1 gene. SM, on the other hand, is usually driven by the genetic mutation KIT D816V.
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