Tryptase

What it isA protease stored in mast cell granules and released during degranulation. Baseline tryptase reflects total mast cell burden; acute tryptase rises sharply during anaphylaxis and returns to baseline within hours.

DoesMarker for mast cell activation and total mast cell number; key in diagnosing anaphylaxis, mast cell activation syndrome, and mastocytosis.

GoodA low, stable baseline tryptase reflects normal mast cell burden and argues against systemic mastocytosis.

BadPersistently elevated baseline tryptase above 20 ng/mL raises concern for systemic mastocytosis. Acute elevation supports a diagnosis of anaphylaxis when measured during a reaction. Hereditary alpha-tryptasemia causes lifelong baseline elevation with variable symptoms.