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Mast Cell Activation Syndrome: when insurers say no, reviewers often say yes
In 17 published external-review decisions involving mast cell activation syndrome, independent physician reviewers overturned the insurer’s denial 41.2% of the time.
Published decisions
17
2001–2026
Overturned
41.2%
7 denials reversed
What the insurer actually argued
Denials fall into different categories, and they don’t succeed equally — so the reason on your letter changes how you should answer it.
| Reason given | Decisions | Overturned |
|---|---|---|
Medical Necessity The plan said the care wasn’t medically necessary. The most common fight, and the most winnable. | 14 | 42.9% |
Experimental/Investigational The plan called the treatment unproven. These turn on published evidence, so the appeal is a literature argument. | 3 | 33.3% |
Typical time to a decision
9 days
Most land between 5 and 20 days
Handled as urgent
64.7%
Expedited when a delay would cause harm
What the reviewers wrote
Excerpts from the independent reviewers’ published findings — the actual reasoning, quoted, not summarised.
Where the denial was overturned
Findings: The physician reviewer found that Nature of Statutory Criteria/Case Summary: A patient has requested authorization and coverage for mast cell infusion regimen composed of slow infusion of 2 liters normal saline, then additional medications including low dose diphenhydramine, ondansetron, famotidine, diphenhydramine, and ketorolac once every 30 to 45 minutes over 4 to 5 hours, including office visit, normal saline infusion, infusion supplies including pump, diphenhydramine, ondansetron, famotidine, diphenhydramine, ketorolac, and intravenous push and infusion services.The records document diagnoses of mast cell activation syndrome and small intestinal bacterial overgrowth. The treating provider recommended infusion therapy including diphenhydramine, diazepam, ondansetron, and famotidine.
Nature of Statutory Criteria/Case Summary: The patient has requested authorization and coverage for Xolair Findings: A study notes that mast cell activation syndrome (MCAS) is defined by typical clinical symptoms such as urticaria, pigmentosa, unexplained hypotension, flushing, organomegaly, a substantial transient increase in serum tryptase level or an increase in other mast-cell-derived mediators, and a response of clinical symptoms to agents that attenuate the production of mast-cell-derived mediators. MCAS may present with skin, gastrointestinal, cardiovascular, respiratory and neurologic symptoms.
Where the denial was upheld
Worth reading too — these show what an appeal has to overcome.
Nature of Statutory Criteria/Case Summary: An enrollee has requested authorization and coverage for Shoemaker Protocol including office visit with qualified provider experienced with the Shoemaker Protocol once every four to six weeks until the Shoemaker Protocol is completed; Welchol 625 mg; liposomal vitamin C 500 mg; vasoactive intestinal peptide nasal spray; epinastine HCL 0.05% two drops twice daily; neuroquadrant magnetic resonance imaging (MRI) without contrast; macron biofilm analysis; nares culture; Singulair 10 mg once daily; Cromolyn 4 ampules twice daily; and cholestyramine non-saccharine 4 grams. CRIS is a controversial constellation of symptoms, which is not currently accepted as a diagnostic disorder.
Nature of Statutory Criteria/Case Summary: An enrollee has requested authorization and coverage for IVIG therapy.The submitted clinical documentation does not support that IVIG therapy is medically necessary for the patient. There are no visit notes demonstrating how diagnoses of mast cell activation syndrome (MCAS), Ehlers-Danlos syndrome or postural hypotension syndrome (POTS) were made. All of the patient’s submitted mast cell studies were normal and the records fail to demonstrate evidence of mast cell activation syndrome.
Figures and quotations on this page come from 42,749 published decisions in the California DMHC Independent Medical Review dataset. These are California outcomes — every state runs an equivalent external review, but the rates here are California’s. Excerpts are quoted verbatim from the public record and describe this condition generally, not any individual case.
How to use this in your appeal
These outcomes come from California’s external review program — an independent physician panel whose decision binds the insurer. Every state has an equivalent, and internal appeals succeed even more often. If your care for mast cell activation syndrome was denied, the published record says the denial is worth fighting.
SOURCE: CALIFORNIA DMHC INDEPENDENT MEDICAL REVIEW OUTCOMES (CHHS OPEN DATA) · DERIVED AGGREGATE STATISTICS ONLY · METHODOLOGY
Not legal or medical advice. Coverage Rights is a self-help tool that helps you prepare your own appeal. For advice about your specific situation, talk to a licensed attorney or your doctor.