Long COVID vs MCAS: symptoms, biomarkers, trials and researchliterature-only comparison
A data-driven comparison of Long COVID and Mast Cell Activation Syndrome (MCAS) built from the Open Source Medicine Foundation biomarker atlases, PubMed literature feeds, ClinicalTrials.gov registry extract and post-acute infection syndrome (PAIS) cohort database.
Mast-cell activation has been proposed as one mechanism of Long COVID, and antihistamines and mast-cell stabilisers are among the agents under investigation. Tryptase and histamine-pathway markers link the two literatures.
No biomarker atlas exists for MCAS, so the biomarker sections below are limited to the other condition. This page compares literature, trials, therapeutics and cohorts.
What each condition is
Long COVID
Also known as: PASC, Post-Acute Sequelae of COVID-19, Post-COVID-19 condition
Long COVID describes symptoms that persist or emerge more than three months after SARS-CoV-2 infection and cannot be explained by another diagnosis. The World Health Organization calls it post-COVID-19 condition; the US National Institutes of Health uses the term PASC. Common features include fatigue, post-exertional symptom exacerbation, cognitive difficulties, orthostatic intolerance, breathlessness and chest pain. Because the triggering infection is known and recent, Long COVID has attracted large prospective cohorts (RECOVER, PHOSP-COVID) and the largest clinical-trial pipeline of any post-infectious illness.
Atlas scope: Molecular, metabolic, and immunological alterations reported in post-acute sequelae of COVID-19 (PASC / long COVID) compared to healthy controls and fully recovered individuals.
OSMF resources: biomarker atlas · literature feed
Mast Cell Activation Syndrome
Also known as: Mast cell activation disorder
MCAS is characterised by episodic, multi-system symptoms (flushing, hives, gastrointestinal upset, wheeze, hypotension) caused by inappropriate release of mast-cell mediators, with laboratory evidence such as a rise in serum tryptase during an episode and a response to mast-cell-directed therapy. Diagnostic criteria remain contested between consensus groups. MCAS is frequently reported alongside POTS, hypermobility and post-infectious illness; OSMF follows it through a literature feed and clinical-trial registry rather than a dedicated biomarker atlas.
OSMF resources: literature feed
Side-by-side summary
| Measure | Long COVID | MCAS |
|---|---|---|
| Biomarkers catalogued | 77 | No atlas |
| Biomarker categories covered | metabolic (23), inflammatory (14), vascular (8), immune (7), coagulation (6), proteomic (5), lipidomic (4), neurological (4), microbiome (4), viral (2) | — |
| Markers with LOINC codes | 25 | — |
| Literature studies tracked | 75 | 75 |
| Most recent tracked study | 07 Jul 2026 | 10 Jul 2026 |
| Registered trials (all statuses) | 341 | 5 |
| Recruiting / not yet recruiting | 81 | 1 |
| Active, not recruiting | 26 | 0 |
| Completed | 150 | 1 |
| Terminated / withdrawn / suspended | 27 | 2 |
| Unknown status | 57 | 1 |
| Named cohorts in PAIS database | 8 | 0 |
| Therapeutic agents tracked | 405 | 11 |
Trial condition matching: Long COVID uses the registry’s mapped condition label; MCAS uses keyword matching on registry condition and title fields. Trials listing both conditions: 1.
Biomarkers catalogued for Long COVID
MCAS has no OSMF biomarker atlas, so no shared-marker matching is possible. The Long COVID atlas lists 77 markers; the 15 most relevant to this comparison are shown (autonomic, immune, inflammatory and vascular categories first).
- Anti-IFN-α autoantibodies Increased immune
- Anti-IFN-ω autoantibodies Increased immune
- Anti-GPCR autoantibodies Increased immune
- β2-microglobulin Increased immune
- Complement C3a / C5a Increased immune
- T cell exhaustion markers Increased immune
- Low naive T cells / High effector memory Mixed / conflicting immune
- Interleukin-6 (IL-6) Increased inflammatory
- Tumor Necrosis Factor-α (TNF-α) Increased inflammatory
- Interleukin-1α (IL-1α) Increased inflammatory
- C-Reactive Protein (CRP) Increased inflammatory
- Soluble CD14 (sCD14) Increased inflammatory
- Flt-1 / sVEGFR-1 Increased inflammatory
- CCL4 (MIP-1β) Increased inflammatory
- Cystatin D (CST5) Increased inflammatory
Browse the full Long COVID atlas.
Overlapping therapeutics under investigation (3)
Agents that appear in registered trials or the OSMF therapeutic-agent database for both Long COVID and MCAS. Inclusion means an agent is being studied, not that it works.
- Cycling
- Montelukast
- Swimming
Trials enrolling both conditions (1)
- NCT07454395 · Is Swimming a More Tolerable Form of Movement for Individuals With Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome? (Suspended)
Research cohorts
Long COVID cohorts (8)
- NIH RECOVER-Adult Cohort prospective non inception, n=15,000, biobank active
- Long COVID Host Genetics Initiative GWAS registry linkage, n=6,450, biobank active
- Patient-Led Long COVID international cohort (Davis 2021) survey, n=3,762, biobank not_applicable
- PHOSP-COVID (UK post-hospitalisation COVID-19) prospective non inception, n=2,320, biobank active
- Jinyintan (Wuhan) COVID-19 discharge cohort (Huang) prospective non inception, n=1,733, biobank unknown
- Bergen COVID-19 home-isolated cohort (Blomberg) prospective inception, n=312, biobank active
- PACVS registry cohort (Semmler/Mundorf) cross sectional, n=191, biobank unknown
- Amsterdam Long COVID muscle-biopsy PEM cohort (Appelman) case control, n=46, biobank unknown
MCAS cohorts (0)
No named cohort for this condition in the PAIS database yet.
Recent research
Latest Long COVID studies
Latest MCAS studies
Frequently asked questions
Can you have both Long COVID and MCAS?
Yes. MCAS is a syndrome diagnosed on clinical criteria and can be diagnosed in someone who also has Long COVID; 1 registered trial in the OSMF registry list both conditions, and they share 3 therapeutic agents under investigation.
How do the biomarker profiles differ?
OSMF does not maintain a biomarker atlas for MCAS, which is diagnosed by physiological or clinical criteria rather than a laboratory panel, so this is a literature-level comparison. Long COVID has 77 catalogued markers across 10 categories (most often metabolic, inflammatory, vascular).
Which has more active clinical trials?
Long COVID has more: 107 active or recruiting trials versus 1 for MCAS (registry snapshot 07 Oct 2026). Totals including completed, terminated and unknown-status studies are 341 for Long COVID and 5 for MCAS. Condition matching for MCAS relies on keyword matching of registry condition fields and may miss trials. Trial counts measure research attention, not treatment efficacy.
Which condition has more recent research?
OSMF tracks 75 recent PubMed-indexed studies for Long COVID (latest 07 Jul 2026) and 75 for MCAS (latest 10 Jul 2026). The feeds hold a rolling window of recent publications, so they indicate current publication pace rather than lifetime output. See the Long COVID feed and the MCAS feed for the full lists.
Are the same treatments being studied for both?
3 agents appear in the trial registry or therapeutic-agent database for both conditions, including Cycling, Montelukast, Swimming. All of these are investigational for these indications; none is an approved treatment for either condition. Overlap usually reflects shared hypotheses (immune modulation, autonomic support, antiviral or anti-inflammatory strategies) rather than demonstrated efficacy.
Which has larger research cohorts?
The PAIS cohort database lists 8 named cohorts for Long COVID and 0 named cohorts for MCAS, the largest being NIH RECOVER-Adult Cohort (15,000 enrolled). Cohorts with stored biospecimens and open external access are the most useful for cross-condition biomarker validation.
Related comparisons
Cite this page
@misc{osmf_longcovid_vs_mcas,
author = {Open Source Medicine Foundation},
title = {Long COVID vs MCAS: symptoms, biomarkers, trials and research compared},
year = {2026},
howpublished = {\url{https://research.opensourcemed.info/compare/long-covid-vs-mcas.html}},
note = {Data as of 2026-10-07}
}Get OSMF research updates
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Last updated 07 Oct 2026 (page build). Underlying data: literature feeds 07 Jul 2026 / 10 Jul 2026; trial registry 07 Oct 2026; atlases 29 Jun 2026 / n/a. Generated by scripts/build_compare_pages.py.