# Chronic Anaphylaxis With Indolent Systemic Mastocytosis: A Case Report

## TL;DR

A patient with a rare mast cell disease and severe anaphylaxis improved after targeted treatment following a confirmed diagnosis.

## Contribution

Demonstrates successful treatment of indolent systemic mastocytosis with avapritinib, a tyrosine kinase inhibitor.

## Key findings

- The patient's quality of life improved after treatment with avapritinib.
- Diagnosis of indolent systemic mastocytosis was confirmed via bone marrow biopsy and genetic screening.

## Abstract

Systemic mastocytosis is a rare, clonal mast cell disease neoplasm driven by the KIT D816V mutation in greater than 95% of cases. The complex clinical presentation of systemic mastocytosis can make diagnosis challenging. Treatment strategies often focus on management of symptoms, but many patients' symptoms are not well controlled on these regimens and have poor quality of life. We report the case of a 35-year-old Caucasian female who suffered repeated life-threatening anaphylactic episodes that greatly decreased her quality of life and that the best supportive care measures failed to control. Following extensive diagnostic evaluations including physical examination, clinical labs, hematology, and next-generation genetic screening, indolent systemic mastocytosis was confirmed by bone marrow biopsy according to World Health Organization 2016 criteria. The patient was subsequently treated with avapritinib, a selective tyrosine kinase inhibitor, after which she reported improved quality of life and physical activity. The diagnosis and optimal management of this complex and rare disease require a multidisciplinary approach combined with effective personalized therapeutic strategies. A confirmed diagnosis of indolent systemic mastocytosis led to the patient receiving an approved targeted treatment, with a favorable outcome. Novel precision therapies and refined diagnostic guidelines are critical to meet the high unmet needs of patients with indolent systemic mastocytosis and improve their quality of life.

ClinicalTrials.gov identifier: NCT03731260