Urticaria pigmentosa, a form of mastocytosis, is an uncommon cutaneous disease characterized by dermal infiltration of mast cells. Clinically, the eruption consists of brownish macules, papules, or vesicles; nodules are rarely present. Urtication of the lesions following mild trauma is a pathognomonic sign. Recently, systemic lesions involving mast-cell infiltrations of bone, bone marrow, liver, spleen, and lymph nodes have been reported. This form has been designated "systemic mastocytosis,'' as opposed to ``mastocytosis cutis'' or simple urticaria pigmentosa. In addition, cutaneous tumorlike mast-cell infiltrates may occur as solitary nodules, particularly in children; this form of mastocytosis has been termed "isolated mastocytoma.''
The lesions of mastocytosis have been found to contain large amounts of histamine, and Pernow and Waldenström1 have reported increased urinary excretion of histamine by patients with urticaria pigmentosa. On the other hand, tissue analysis has revealed only trace amounts of serotonin, and Davis, Lawler, and Higdon2 reported
DEMIS DJ, WALTON MD, HIGDON RS. Histaminuria in Urticaria Pigmentosa: A Clinical Study and Review of Recent Literature with Definition of the Mastocytosis Syndrome. Arch Dermatol. 1961;83(1):127–138. doi:10.1001/archderm.1961.01580070133015
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