Distinguishing MCAS from Idiopathic Anaphylaxis

I agree the lines are very blurred. I reached out to Dr. Melody Carter, a mast cell disease expert. Her response is below.

You are correct with your interpretation of the criteria for these disorders. Because of the categorization of the current entities, IA is considered under the broad category of MCAS.

Although the diagnosis is sometimes difficult to delineate, it is important to note that the therapy for clonal and non-clonal mast cell disease is the same. Anti-mediator therapy such as antihistamines are used in all variants. Cytoreductive therapy is reserved for patients diagnosed with clonal mast cell disease such as mastocytosis by WHO criteria with severe manifestations of the disease.

Below are some articles that may be helpful in determining if a patient is a candidate for a bone marrow procedure. Patients with venom anaphylaxis have a higher rate of clonal mast cell disease and are considered separately from patients with idiopathic anaphylaxis.

Melody C. Carter, MD, Avanti Desai, MSc, Hirsh D. Komarow, MD, et al. A distinct biomolecular profile identifies monoclonal mast cell disorders in patients with idiopathic anaphylaxis. J Allergy Clin Immunol 2018;141:180-8.)

Valent P. Mast cell activation syndromes: definition and Classification. Allergy 2013; 68: 417–424.

Theo Gülen, MD, PhD, Christopher Ljung, BSc, Gunnar Nilsson, PhD, and Cem Akin, MD, PhD. Risk Factor Analysis of Anaphylactic Reactions in Patients with Systemic Mastocytosis. J Allergy Clin Immunol Pract 2017;5:1248-55

Alvarez-Twose, D. Gonzalez-de-Olano, L. Sanchez-Munoz. Validation of the REMA Score for Predicting Mast Cell Clonality and Systemic Mastocytosis in Patients with Systemic Mast Cell Activation Symptoms. Int Arch Allergy Immunol 2012;157:275–280

Respectfully submitted
Jeffrey Demain, MD, FAAAAI with recognition and appreciation for Dr. Melody Carter