Cholinergic urticaria, a new pathogenic concept: hypohidrosis due to interference with the delivery of sweat to the skin surface.

BACKGROUND: Acetylcholine has been suspected to be a pathogenetic factor for cholinergic urticaria (CU), without definite evidence. In contrast, there are scattered reports of CU associated with acquired generalized hypohidrosis. We have recently examined 2 patients with CU in both of whom we noticed the presence of extensive hypohidrosis that occurred only in winter.

OBJECTIVE: In these 2 patients, acquired hypohidrosis due to superficial obstruction of the acrosyringium was suspected as the cause. Both case 1, a 22-year-old Japanese man, and case 2, a 21-year-old Japanese man, began to have anhidrosis and numerous red macules on their body whenever they felt hot in winter. These symptoms ceased to appear in summer.

METHODS: We studied histologically their lesional skin in addition to provocation tests for CU.

RESULTS: The diagnosis of CU was confirmed by the provocation of typical wheals after physical exercise in both cases. Histological study revealed findings suggestive of the presence of occlusion of the superficial acrosyringium.

CONCLUSION: We think that such a hypohidrosis due to occlusion of superficial sweat ducts may also play a role in many other patients with CU of unknown etiology that becomes exacerbated in winter when sweating is not a frequent event.