A Real-World Cross-Sectional Study on Suspected Mast Cell Activation Syndrome: Multiple Heterogeneous Symptoms...

A variety of clinical signs and symptoms have been described in patients suspected of having mast cell activation syndrome (MCAS), however, symptom patterns and linked organ systems were not yet described.

This cross-sectional online survey included adults with physician-diagnosed self-assessed or suspected MCAS between June and September 2021. Symptoms were collected as free-text responses, and coded using the Medical Dictionary for Regulatory Activities (MedDRA). These data were then analyzed using an unsupervised machine learning approach to identify distinct participant clusters. Patient-reported outcome measures (PROMs), including the PHQ-2, GAD-7, and SF-36, were used to assess mental health symptoms and health-related quality of life.

A total of 592 patients (mean age 45 years, 90% female) reported 400 symptoms in 58 categories. The hierarchical clustering algorithm failed to identify distinct patient clusters. We identified 256 (43%) patients with signs and symptoms aligning with the diagnostic criteria for MCAS including the most prevalent symptoms. Overall, patients infrequently reported mast cell-mediated skin symptoms, such as pruritus (13%), wheals (9%), flushing (7%), or angioedema (1%). We identified patients with comorbid signs of depression (39%), general anxiety (34%), and impaired quality of life (28%).

Patients with suspicion of MCAS exhibit highly heterogeneous symptoms, whereas almost 50% report symptoms corresponding to the first diagnostic criterion for MCAS. Because over a third of the patients were tested positive for other diseases, we recommend considering common and more treatable diagnoses when evaluating patients with suspected MCAS.