When to Refer a Patient with Suspected ISM to an Allergist, with Patricia Lugar, MD

Following OncologyLive’s workshop on November 21, 2024, called “Best Practices in Managing Indolent Systemic Mastocytosis (ISM),” HCPLive spoke with participant Patricia Lugar, MD, allergy and immunology specialist at the Duke Asthma, Allergy, and Airway Center, to continue the discussion on allergic manifestations and diagnostic clues of ISM.

Lugar said an allergic reaction could indicate the presence of a mast cell disease. For instance, while anyone could have an allergic reaction to bees, people with a mast cell disease may present mostly cutaneous symptoms—flushing, blotchiness in the skin, and a visible rash. It is also common for people with mast cell disorders to have syncope, lightheadedness, shortness of breath, tachycardia, and some cardiopulmonary symptoms along with cutaneous symptoms.

But when should a clinician refer a patient with suspected or confirmed ISM to an allergist?

“I like to see patients in all steps of suspicion,” Lugar said. “I love it when the GI doc, the primary care group, or whoever’s seeing the patient [and] knows the patient well, is first availing the patient for a constellation of symptoms and raises this question to grab a tryptase. That helps me out quite a bit because it lets me know what my level of suspicion might be and how to do the diagnostic evaluation next.”

A serum tryptase test helps distinguish clonal mast cell disorders, such as systemic mastocytosis, and other mast cell disorders. Even if the patient has no mast cell disorder, an allergist can still treat the reactions.

However, if it is a suspected mast cell disease, an allergist can refer the patient to colleagues who can provide a true diagnosis. For example, a patient may need a bone marrow exam.

Lugar said some misconceptions about ISM are what can and cannot trigger allergic reactions in someone with a clonal mast cell disorder. She added how it is challenging when patients ask, “Can you do a skin test for that?” or “Tell me everything I’m allergic to because I want to start a new medication.”

“Well, I wish I could, but I can't,” Lugar said. “I can't tell you what statin they're going to tolerate, what blood pressure medicine they're going to tolerate, because we don't have direct guidance often on how the exposures are interacting with this particular patient… It's a little bit of trial and error.”

For more insights on diagnosing indolent systemic mastocytosis as well as to learn more about managing indolent systemic mastocytosis, read Best Practices in Managing Indolent Systemic Mastocytosis (ISM): Disease Mechanisms, Diagnostic Challenges, and Multidisciplinary Treatment Strategies here.

Relevant disclosures for Lugar include Blueprint Medicines Corporation, Grifols USA, BioCryst US Scales, and Grifols Shared Services North America.

References

1. Derman, C. Indolent Systemic Mastocytosis’ Diagnostic Clues, with Patricia Lugar, MD. HCPLive. March 19, 2025. https://www.hcplive.com/view/indolent-systemic-mastocytosis-diagnostic-clues-with-patricia-lugar-md. Accessed March 19, 2025.

2. Best Practices in Managing Indolent Systemic Mastocytosis (ISM). OncLive. February 19, 2025. https://www.onclive.com/view/best-practices-in-managing-indolent-systemic-mastocytosis-ism-. Accessed March 18, 2025.