Clinical Background
Systemic mastocytosis, the most common mast cell disease, is associated with mast cell hyperplasia and elevated histamine and tryptase levels.
Epidemiology
- Incidence - rare disease
- Age - except for cutaneous mastocytosis, the disease predominates in adults
Classification
- WHO classification of mastocytosis
- Cutaneous mastocytosis
- Indolent systemic mastocytosis
- Systemic mastocytosis associated with clonal cell lineage disease
- Aggressive systemic mastocytosis
- Mast cell leukemia
- Mast cell sarcoma
- Extracutaneous mastocytosis
Pathophysiology
- Mutation in the kit tyrosine kinase domain D816 V gene is the main cause of the disease process
- This gene, in combination with others, exerts proliferation, which enhances uncontrolled mast cell proliferation
- Mast cells produce histamine and tryptase
- Disease process is marked by increased levels of both histamine and tryptase
- Increased histamine concentrations in plasma and urine may indicate:
- Allergic response (anaphylaxis)
- Carcinoid tumors, particularly of gastric origin
- Chronic myeloproliferative disorders
- Urticaria pigmentosa or systemic mastocytosis
- Increased tryptase levels may be occur in:
- Mastocytosis
- Urticaria
- Asthma
- Anaphylaxis
- Tryptase levels in mast cell diseases typically rise within 1 hour and remain elevated 4-6 hours
- In contrast, histamine levels peak at 5 minutes and return to baseline by 30 minutes
- Beta-tryptase is usually elevated in systemic anaphylaxis of sufficient severity to cause hypotension
Clinical Presentation
- Recurrent episodic flushing
- Anaphylaxis
- Tachycardia
- Nausea, emesis, diarrhea, hepatomegaly
- Wheezing, hives and angioedema are very uncommon
- Skin
- Urticaria pigmentosa
- Individual hyperpigmented and telangiectatic papules
- Urticaria pigmentosa
- Prognostic indicators for systemic mastocytosis
- B - elevated tryptase >200 ng mL, dysmyelopoiesis and organomegaly
- C - evidence of impaired organ function (hepatic, gastrointestinal, bone marrow)
See Also
