Meyerson phenomenon around mastocytoma.
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In the current case, the prevalent localization of atopic dermatitis above and around mastocytoma is to be considered a Meyerson phenomenon. By this term we mean an eczematous type dermatitis, i.e. with epidermal involvement, which is also or exclusively localized around one or more pre-existing skin infiltrative lesions. The infiltrated lesion is often a melanocytic nevus, but it can be a seborrheic wart, a squamous or basal cell carcinoma, a keloid, an insect bite (4) or, as in the current case, a mast cell tumor.
The pathogenesis of Meyerson phenomenon is not known and is however different from other similar conditions such as halo nevus. The Meyerson phenomenon is different from halo nevus both because it is not directed only against a melanocytic nevus, and because, when it is localized on a melanocytic nevus, it does not damage it. It is also different from eczema that is localized on the salmon patch or on other vascular lesions, in which the determining factor is vasodilation.
It is possible that the eczematous reaction of Meyerson phenomenon prefers different or anyway raised areas of skin; this event also occurs for other dermatitis such as erythema multiforme (3) or pityriasis rosea (2).
Interesting is the prevalence of Meyerson phenomenon in the trunk (5), as in the present case, probably influenced by the fact that the target lesions are in order of frequency nevi and seborrheic warts, but probably also determined by other factors: for example in one case by Girard et Al. (1) patches of nummular eczema appear on the trunk, upper and lower limbs, but only on the trunk are localized in the perinevic area.