MAST CELL DISEASES
Mastocytosis occurs from birth to adulthood; adult-onset cases are more severe.
The WHO separates mastocytosis into 3 categories:
• Cutaneous mastocytosis, seen in children, regresses over time. Mast cell degranulation enzymes (histamine and tryptase) cause pruritus.
• Systemic mastocytosis is a clonal proliferation of mast cells associated with a KIT mutation; ≥1 organs are involved, as are the skin and bone marrow. The WHO now classifies systemic mastocytosis as one of the myeloproliferative neoplasms.
Variants include some rare leukemias.
Diagnosis is made with bone marrow biopsy and molecular analysis.
• Localized extracutaneous mast cell neoplasms can be benign (mastocytoma) or malignant (sarcoma).