Idiopathic mast cell activation syndrome is more often suspected than diagnosed—A prospective real-life study, 2023, Buttgereit et al.

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https://onlinelibrary.wiley.com/doi/full/10.1111/all.15304

Idiopathic mast cell activation syndrome is more often suspected than diagnosed—A prospective real-life study

Thomas Buttgereit, Sophie Gu, Leonor Carneiro-Leão, Annika Gutsche, Marcus Maurer, Frank Siebenhaar
First published: 01 April 2022

https://doi.org/10.1111/all.15304


Abstract
Background
Idiopathic mast cell activation syndrome (MCAS) is characterized by three diagnostic criteria: (1) episodic mast cell (MC)-driven signs/symptoms of at least two organ systems in the absence of clonal MC expansion and definite triggers, (2) episodic increase in tryptase, and (3) response to MC-targeted treatment. Many patients believe they have MCAS, but how often this is the case remains unknown.

Methods
We prospectively investigated patients with suspected MCAS (n = 100) for the diagnostic criteria including baseline tryptase, KIT D816V mutation, and patient-reported outcome measures (PROMs) over the course of 12 weeks. Comorbid depression and anxiety were explored with the Hospital Anxiety and Depression Scale (HADS).

Results
In 53% of our patients (80% females), suspicion of MCAS was based on self-evaluation. In total, patients reported 87 different symptoms, mostly fatigue (n = 57), musculoskeletal pain/weakness (n = 49), and abdominal pain (n = 43), with overall high disease activity and impact. Two of 79 patients had increased tryptase (by >20% +2 ng/ml) following an episode. Only 5%, with any of the PROMs used, showed complete response to MC-targeted treatment. Depression and anxiety disorders were frequent comorbidities (n = 23 each), and 65 patients had pathological HADS values, which were linked to high disease impact and poor symptom control.

Conclusion
Mast cell activation syndrome was confirmed in only 2% of patients, which implies that it is not MC activation that drives signs and symptoms in most patients with suspected MCAS. There is a high need for comprehensive research efforts aimed at the identification of the true underlying pathomechanism(s) in patients with suspected MCAS.

 

A rate of 2% of an 'elevated level' sounds pretty much expected from a normal distribution - i.e. what you would get with normal people. And with an episodic condition 5% being better would presumably happen anyway and people with all sorts of unrelated episodic conditions would be better after mast cell treatment too.

The strong impression is that if this is what 'MCAS' consists of, it isn't worth having a name.