Mast Cell Activation Syndrome

Mast Cell Activation Syndrome is indexed under Long COVID & Post-Infectious Syndromes, Immune Dysregulation. Also known as MCAS.

US prevalence

~17% of general population per some estimates (highly contested); clinically significant subset much smaller Source: AAS; controversial estimates. This figure comes from a professional society, registry, or study rather than a federal source. Label: REPORTED.

ICD-10-CM codes

D89.40

Typical onset

Any age; increasingly recognized post-COVID

Course

managed

Body systems

immunologic, dermatologic, gastrointestinal

Sex differences

F:M ~2-3:1

Racial and ethnic differences

Limited data

What this page does not establish

These figures describe populations, not individuals, and none of them is a diagnosis or a treatment recommendation. Prevalence estimates are approximate and reflect published ranges. Disparity figures are reported patterns, not causes.

Taxonomy last reviewed 2026-05-19. Each figure on the interactive page carries its own source and retrieval date, which can be later than this review.

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