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Basics ⬇

Clinical Manifestations ⬆ ⬇

Solitary mastocytoma !!navigator!!

  • Presents at birth or within the first year of life as a skin-colored to yellow-orange-red papule or plaque (Fig. 8.8).

  • Lesions develop an itchy erythematous urticarial wheal when rubbed or stroked; this change is referred to as Darier sign, and represents mast cell degranulation induced by physical stimulation (Fig. 8.9A,B). This reaction can be elicited after gentle mechanical irritation such as with rubbing of a tongue blade or the blunt end of a cotton tip swab.

  • A similar reaction may be provoked by other everyday triggers (see Table 8.1).

  • Occasionally, stroking or rubbing can result in blistering or systemic symptoms including flushing or gastrointestinal disturbance.

  • Lesions tend to spontaneously involute over several years.

  • Sometimes multiple mastocytomas may be present.

Urticaria pigmentosa (also called maculopapular cutaneous mastocytosis) !!navigator!!

  • This is the most common presentation of childhood mastocytosis.

  • Presents with multiple tan to red-brown macules and papules usually on the thighs, arms, trunk, and genitalia, but may occur anywhere, including the mucous membranes.

  • Lesions can also present as flat macules resembling café au lait spots (Fig. 8.10).

  • The palms and soles are usually spared.

  • In children the face and scalp may be involved.

  • Affected persons may have tens to hundreds of lesions that range in size from a few millimeters to several centimeters.

  • Darier sign is positive and dermatographism (see Chapter 27: Diseases of Cutaneous Vasculature) may be present.

  • Pruritus is the most common symptom resulting from mast cell degranulation and occurs in response to triggers such as changes in temperature, hot showers, friction or emotional stress (see Table 8.1).

  • Occasionally associated with systemic mastocytosis. The most commonly involved extracutaneous site is the gastrointestinal tract followed by the skeletal system.

  • In most cases, lesions improve or resolve completely by adolescence.

Diffuse Cutaneous Mastocytosis !!navigator!!

  • Least common, this is a systemic variant of childhood mastocytosis characterized by diffuse infiltration of the skin by mast cells manifested as thickened doughy, yellowish skin.

  • Usually accompanied by intense pruritus and flushing and is often associated with systemic symptoms including elevated temperature, vomiting, diarrhea, abdominal pain, or occasionally shock.

Outline

Diagnosis ⬆

  • Eliciting the Darier sign can aid in the diagnosis of all forms of cutaneous mastocytosis.

  • If the diagnosis is in doubt, a skin biopsy will show an accumulation of mast cells in the dermis, which can be highlighted by Giemsa, toluidine blue, or tryptase antibodies.

  • A serum tryptase level and/or urinary n-methylimidazoleacetic acid, a histamine metabolite, are useful chemical markers for the disease and will be elevated in systemic involvement or be suggestive of a high disease burden.

Point-Remember-icon.jpg Points to Remember

  • Risk factors for systemic disease include: children with the onset of skin lesions beyond 2 years of age and those who have persistence of skin lesions beyond adolescence.

  • Avoid physical irritation of a solitary mastocytoma to prevent symptoms.

  • Information for patients and families about mastocytosis and mast cell degranulators can be found at www.mastokids.com.

Diagnosis-icon.jpg Differential Diagnosis

Solitary Mastocytoma
Insect Bite Reaction

  • Pink edematous itchy papule or plaque at the site of a bite.

  • Occurs on exposed areas of skin and usually resolves in days to weeks.

Herpes Simplex

  • Recurrent bullous reactions can mimic a recurrent herpes infection.

  • HSV culture and/or Tzanck preparation may be positive and lesions are generally painful.

Urticaria Pigmentosa

  • Café au lait macules.

  • Asymptomatic macules.

  • Negative Darier sign.

Management-icon.jpg Management

  • Solitary mastocytomas usually involute after several years and the lesions of urticaria pigmentosa resolve completely or improve during adolescence in the vast majority of patients. The tendency for a blistering reaction disappears in 1 to 3 years.

  • Families should be educated on the natural history of the condition and its tendency to spontaneously resolve by adolescence, often much sooner.

  • Families should be counseled on the triggers of mast cell degranulation and on avoiding these triggers if possible.

  • Patients with extensive cutaneous disease or elevated baseline tryptase levels may be at increased risk of anaphylaxis from a variety of triggers. These patients should have a yearly serum tryptase level, complete blood count (CBC) with differential, and a chemistry panel including alkaline phosphatase.

  • Treatment is primarily symptomatic. Patients with higher tryptase levels (>6 ng/mL) are more likely to be symptomatic and require daily treatment.

  • Potent topical steroids under occlusion such as clobetasol 0.05% cream have been noted to improve solitary mastocytomas.

  • Nonsedating antihistamines such as cetirizine, loratidine, or fexofenadine are a good initial treatment of choice.

  • In patients with extensive involvement or symptoms the addition of the classic H1 antagonists, diphenhydramine or hydroxyzine, or H2 antagonists such as cimetidine or ranitidine may be considered.

  • Oral cromolyn sodium has been beneficial in patients with gastrointestinal involvement.