3.2.8 Cutaneous Mastocytosis
Grading & Level of Importance: B
Mastocytosis, mast cell disease.
Rare disease, most common in children. Prevalence 0.1 to 0.8% of dermatology consultations.
65% are observed in children below 15 years. Two peaks of incidence, one between 6 months and 2 years (55%) and one between 20 and 40 years (35%).
Proliferation of mast cells in the skin.
Aetiology & Pathogenesis
It is frequently caused by mutations in the KIT gene (KIT D816V) and is most often sporadic. MRGPRX2 activates mast cells, which in turn release tryptase and histamine with local or systemic symptoms.
Signs & Symptoms
Urticaria pigmentosa (maculopapular mastocytosis): many red-brown, maculopapular lesions, with variable flushes and pruritus (most common form). Diffuse cutaneous mastocytosis: diffuse erythema, skin infiltration, blistering (rare, in the first month of life). Localized mastocytosis (mastocytoma) is a single lesion (or sometimes 1-3 lesions), most often found in children. Mastocytosis skin lesions respond with an urticarial reaction spontaneously or after irritation (Darier's sign: wheal, erythema, itch). Furthermore, a so called idiopathic mast cell activation syndrome (MACS) was recently introduced as an entity within the mast cell disorders.
Cutaneous mastocytosis (urticaria pigmentosa and diffuse cutaneous mastocytosis) shows a disseminated appearance on the entire body. Mastocytoma is a unique lesion, or multiple (generally 1 to 3) lesions localized anywhere on the skin. MACS is a mast cell products release disorder without specific localization without diffuse increase of mast cells, as in the diffuse type.
The 2016 updated current WHO classification of mastocytosis identifies 3 forms of cutaneous mastocytosis: urticaria pigmentosa, diffuse cutaneous mastocytosis, and mastocytoma.
Laboratory & other workups
Serum tryptase levels are correlated with the mast cell tumor burden. A complete blood count is useful to screen for hematologic (medullary) involvement.
Dense perivascular infiltrates of mast cells which stain positively with Giemsa, toluidine blue (heterochromasia) or chloroacetate esterase (Leder-stain). Immunohistochemistry to stain mast cells (anti-CD117=KIT, anti-tryptase, and anti-CD25 antibodies).
If the disease appears in childhood, spontaneous remission is frequent. The adult version is generally clinically stable but mast cells may proliferate and lead to systemic symptoms.
In adults, flushes, hives, diarrhoea, vomiting, headache, depression, breathing problems, osteoporosis, visceral involvement, anaphylaxis (rare). Worsening of symptoms may be provoked by alcohol and certain food or drugs.
Diagnosis is based on typical clinical features and confirmed by histopathology. At baseline, no additional workup is required in children. Serum tryptase levels, complete blood count, abdominal ultrasonography and osteodensitometry are performed in adults. In diffuse type of mastocytosis and KIT anomaly a bone marrow aspiration is indicated.
Prevention & Therapy
None is required if no functional disturbance. Non-sedating antihistamines; H2 blockers or cromoglycate for gastrointestinal symptoms; PUVA; short-term high-potency topical glucocorticoids. Written information about the risk of anaphylaxis +/- adrenaline syringe in high risk cases.
Malignant transformation very rare.
- Statement 1 Part of the evaluation of patients with urticaria pigmentosa includes prick testing.
- Which form of therapy is not indicated for urticaria pigmentosa in adults?
- Statement 1 Urticaria pigmentosa is an uncommon form of chronic urticaria
- Statement 1 The lesions seen in urticaria pigmentosa should be regularly checked with dermatoscopy
- Which of the following foods, medications and situations can trigger histamine release in patients with urticaria pigmentosa?
- Urticaria pigmentosa can appear in childhood and adult life. The childhood form is characterized by ...
- Statement 1 The picture shows a lesion of urticaria pigmentosa which has been rubbed
Further Images / DOIA
- C. Di Raimondo, E. Del Duca, D. Silvaggio, et al.: Cutaneous mastocytosis: A dermatological perspective (2020)
- A. Abid, M.A. Malone, K. Curci: Mastocytosis (2016)
- K. Hartmann, L. Escribano, C. Grattan, et al.: Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology (2016)
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