Mastocytosis

Aka: Mastocytosis, Cutaneous Mastocytosis, Systemic Mastocytosis, Urticaria Pigmentosa, Maculopapular Cutaneous Mastocytosis, Diffuse Cutaneous Mastocytosis, Mastocytoma, Skin Mastocytoma

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II. Definitions

  1. Mastocytosis
    1. Abnormal proliferation and accumulation of Mast Cells within various organ systems
    2. May be limited to skin Mast Cell accumulation (Cutaneous Mastocytosis)
    3. May be diffusely increased in Bone Marrow, Spleen, and liver (Systemic Mastocytosis)

III. Pathophysiology

  1. Abnormal proliferation and accumulation of Mast Cells within various organ systems
  2. High number of Mast Cells degranulate, releasing vasoactive agents (esp. Histamine)

IV. Types

  1. Cutaneous Mastocytosis
    1. Isolated skin Mast Cell accumulation
    2. Most cases are in children (80% of cases are age <1 year old)
    3. Subtypes
      1. Maculopapular Cutaneous Mastocytosis or Urticaria Pigmentosa (75%)
      2. Solitary Mastocytoma (20%)
        1. Mast Cell tumor of the skin, subcutaneous tissue or Muscle Tissue
      3. Diffuse Cutaneous Mastocytosis (5%)
  2. Systemic Mastocytosis
    1. Diffusely increased Mast Cells in Bone Marrow, skeletal system, Spleen, and liver
    2. Most cases are in adults (95% of adult cases)

V. Causes: Triggers for Mast Cell Degranulation

  1. Medications (e.g. Opioids, NSAIDs, iodinated contrast, Vancomycin, general Anesthesia)
  2. Physical stimuli (e.g. Exercise, extremes of Temperature, emotional stress)
  3. Surgical procedures
  4. Bites and Stings (e.g. Insect Bites, Animal Bites)

VI. Findings: Cutaneous Mastocytosis

  1. Frequently accompanied by systemic symptoms below
  2. Pruritus
  3. Darier Sign
    1. Skin lesion is rubbed with a Tongue depressor using moderate pressure five times
    2. Positive test if results in a wheal and flare reaction
  4. Maculopapular Cutaneous Mastocytosis (Urticaria Pigmentosa)
    1. Red-Brown or pink Macules or Papules with widespread and asymmetric distribution

VII. Findings: Systemic Mastocytosis

  1. Flushing
  2. Pruritus
  3. Nausea
  4. Vomiting
  5. Abdominal Pain
  6. Diarrhea
  7. Headache
  8. Anaphylaxis (uncommon, severe cases)

VIII. Labs

  1. Complete Blood Count
    1. Anemia -mild to moderate (50% of cases)
    2. Eosinophilia (25% of cases)
    3. Monocytosis (50% of advanced cases)
  2. Mastocytosis specific lab markers
    1. Serum Tryptase >20 ng/ml (systemic mastocytocytosis)
    2. Urine 24 hour collection for Histamine or Histamine Metabolites
  3. Skin Biopsy of Maculopapular Cutaneous Mastocytosis (Urticaria Pigmentosa)
    1. Mast Cell aggregation
  4. Bone Marrow Biopsy
    1. Spindle-shaped Mast Cells
    2. Distribution in perivascular, peritrabecular and intertrabecular areas
  5. Other advanced testing
    1. KIT Gene Mutation Analysis

IX. Management

  1. Symptomatic Management
    1. Antihistamines for Pruritus
    2. Aspirin for Flushing (adults)
  2. Urticaria Pigmentosa
    1. PUVA
    2. Corticosteroids (severe cases)
  3. Gastrointestinal Symptoms
    1. Mast Cell Stabilizers (e.g. Disodium Chromoglycate)
    2. Proton Pump Inhibitors or H2 Blockers (e.g. Pepcid)

X. References

  1. Castells and Akin in Saini (2017) Mastocytosis Evaluation and Diagnosis, UpToDate, accessed 10/5/2020
  2. Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL, p. 30-1
  3. Green (2022) Am Fam Physician 105(6): 671-2 [PubMed]

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