IN THIS ARTICLE
- Clinical presentation
- Disease triggers
- Outcome for the case patient
A 4-month-old white boy is brought to the allergy office for evaluation of a lesion on his back, first noticed when he was one month old. His parents report that on two separate occasions he developed a bright red, whole-body rash that resolved on its own. He is described as a “fussy” baby who has been on both milk- and soy-based formulas. Aside from mild eczema and infantile seborrheic dermatitis, his medical history is unremarkable.
Physical examination reveals a reddish, 3-cm plaque on his left upper back that, when stroked, exhibits an immediate urticarial response. The patient is given cetirizine in the office and within 45 minutes, the flushing resolves. A normal tryptase level is obtained. The patient is diagnosed with a solitary mastocytoma.
Mast cells play a central role in allergic rhinitis, asthma, eczema, and anaphylaxis; they are also a vital component in the inflammatory process. Cutaneous mastocytosis is a pathologic increase in mast cells that, when degranulated, release histamine and tryptase.1 Histamine is produced equally by both mast cells and basophils, while the production of tryptase is relatively specific to mast cells. An elevated tryptase level is indicative of mast cell activation. The signs and symptoms associated with cutaneous mastocytosis are due to the release of these mediators.2
While there is no gender bias for cutaneous mastocytosis, there is a bimodal distribution: Children from birth to age 2 account for 55% of cases, whereas 35% of cases occur in those older than 15—the remaining 10% are between these ages.1 During the first year of life, 60% to 80% of patients with cutaneous mastocytosis will develop lesions. Familial cases are rare.2
The presentation of cutaneous mastocytosis can vary. It is often mistaken for common childhood rashes such as poison ivy, eczema, or hives. The effects of histamine and tryptase cause children to present with pruritus, flushing, and headache. Gastrointestinal symptoms, such as abdominal pain and diarrhea, can also occur as a result of histamine release. Symptoms can occur spontaneously or be induced by certain triggers (see Table).3
There are three types of cutaneous mastocytosis: urticarial pigmentosa (UP), solitary mastocytoma, and diffuse cutaneous mastocytosis (DCM). UP is the most common, representing 70% to 90% of all cases.3 It typically manifests as multiple red, brown, or yellow lesions that are small (usually < 2 cm). A positive Darier sign (the formation of a wheal and flare after stroking one or several lesions) is common in these patients.2,3
Solitary mastocytomas are single, indurated, red-brown macules, papules, or plaques.4 Frequently seen on the trunk, extremities, head, or neck, these lesions resemble UP but are larger (up to several centimeters in diameter).2,4 A positive Darier sign is elicited in approximately 50% of these patients.4 Solitary mastocytomas are seen in 10% to 15% of children with cutaneous mastocytosis.4
DCM accounts for only 1% to 3% of cases and typically involves the entire skin, which is usually thick, with a normal or yellowish brown color.3 Affected patients may experience blistering and bullae. Severe symptoms, including whole-body flushing, pruritus, diarrhea, intestinal bleeding, hypotension, anemia, and hypovolemic shock, can occur; deaths have been reported.2