Cutaneous mastocytosis, or mastocytosis that affects the skin, is diagnosed based on the appearance of the skin and a skin biopsy. The biopsy looks for an unusually high amount of mast cells in the skin.
Systemic mastocytosis, or mastocytosis that affects other tissues, is diagnosed based on a bone marrow examination. The examination determines whether or not there are too many mast cells in the marrow.
Other tests often used to diagnose mastocytosis include measurement of the tryptase protein from mast cells in the blood and tests for genetic mutations that doctors associate with the disease.