QShould I prescribe an EpiPen to my pediatric patients with cutaneous mastocytosis?

Mastocytosis is a unique and interesting disease which can involve both the skin and internal organs. Pediatric cutaneous mastocytosis is principally divided into 3 distinct morphologies: diffuse cutaneous mastocytosis, solitary mastocytoma and maculopapular cutaneous mastocytosis (formerly known as urticaria pigmentosa). Mastocytosis, which is fundamentally an increase in the number of mast cells in any given tissue, can lead to anaphylaxis through mast cell degranulation through release of its contents including histamine, prostaglandins and leukotrienes.

The range for anaphylaxis in patients with pediatric mastocytosis in the literature ranges from 0-9% with an average frequency of 3.9% and is difficult to predict reliably.¹ Diffuse cutaneous mastocytosis, the most extensive form of cutaneous disease, has been reported as one of the risk factors for anaphylaxis if the total skin involvement is > 45 % body surface area (BSA) and the density is > 15% BSA (utilizing the patient’s palm as 1% BSA).¹ The maximum density of skin involvement is defined as percentage of surface of involved skin to the total skin surface in each patient in the area of highest density of disease.

According to this criterion, the risk of anaphylaxis is increased in pediatric cutaneous mastocytosis patients if their total body BSA is greater than 45% and the densest area of disease on the skin is 15% or greater of the total body surface area. Therefore, according to the literature, providers do not necessarily have to prescribe an EpiPen unless the patient has severe cutaneous involvement as per the above criterion. Patients should of course be counseled on which medications to avoid. A helpful mnemonic to remember this is “PROMS” (Polymyxin, Radiocontrast dye/Rum (alcohol), Opioids, Muscle relaxants, Salicylates/nSaidS). Acetaminophen is safe to take for a mastocytosis patient.²

References:

1. Brockow K, Plata-Nazar K, Lange M, Nedoszytko B, Niedoszytko M, Valent P. Mediator-Related Symptoms and Anaphylaxis in Children with Mastocytosis. Int J Mol Sci. 2021;22(5):2684. doi:10.3390/ijms22052684
2. Triggers of Anaphylaxis in Mastocytosis Patients: Evidence of the Current Drug-Avoidance Recommendation | Current Treatment Options in Allergy. Accessed May 23, 2024. https://link.springer.com/article/10.1007/s40521-023-00349-2