To the Editor.—
In his report of alopecia mucinosa with neurofollicular changes, Burket1 cites an explanation for the delayed blanch phenomenon (of acetylcholine injected into atopic skin), which was postulated by Lobitz and Campbell2 in their report. This explanation, postulating a paradoxic vasoconstriction in the atopic individual, has been supplanted by the theory that the delayed blanch represents edema fluid in the skin that appears after extreme vasodilatation, thus obscuring the erythema. Ramsey,3 with the use of a photoelectric pulsimeter, and Copeman and Winkelmann,4 with the use of Evans Blue dye intravenously injected, have demonstrated such an outpouring of edema fluid. Ramsey also found evidence of vasodilatation, not vasoconstriction, at the site of methacholine injection.The delayed blanch in alopecia mucinosa may be explained, however, by the phenomenon of denervation supersensitivity.5 This phenomenon is defined as a reduction in the threshold of responsiveness of
Stone SP. Delayed Blanch in Alopecia Mucinosa. Arch Dermatol. 1975;111(1):132. doi:10.1001/archderm.1975.01630130134031
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