CHOLINERGIC

 

 URTICARIA

 

 

Cholinergic urticaria develops after an increase in core

body temperature, such as during a warm bath, prolonged exercise, or episodes of fever.¹⁰⁵ The highest prevalence is observed in individuals aged 23 to 28 years. The eruption appears as distinctive, pruritic, small, 1- to 2-mm wheals that are surrounded by areas of erythema . Occasionally, the lesions may become confluent, or angioedema may develop. Systemic features include dizziness, headache, syncope, flushing, wheezing, shortness of breath, nausea, vomiting, and diarrhea. An increased prevalence of atopy has been reported. The intracutaneous injection of cholinergic agents, such as methacholine chloride, produces a wheal with satellite lesions in approximately one-third of patients. Alterations in pulmonary function have been documented during experimental exercise challenge¹⁰⁸ or after the inhalation of acetylcholine, but most patients are asymptomatic.

A major sub-population of patients with cholinergic urticaria have a positive skin test result and in vitro histamine release in response to autologous sweat. It is not clear whether or not this is IgE mediated, and any antigen present in sweat is unidentified. This is the same sub-population with a positive methacholine skin test result with satellite lesions and a non-follicular distribution of the wheals. The remaining patients had negative results on autologous sweat skin tests and no in vitro histamine release. Results of the methacholine skin test are negative for satellite lesions and the hives tend to be follicular in distribution.

Familial cases have been reported only in men in four families. This observation suggests an autosomal dominant or sex-linked pattern of inheritance. One of these individuals had co-existing dermographism and aquagenic urticaria.

After exercise challenge, histamine and factors chemotactic for eosinophils and neutrophils are released into the circulation.^88,108 Tryptase has been detected in lesional suction-blister aspirates. The urticarial response has been passively transferred on one occasion; however, most other attempts to do so have been unsuccessful.

Cold urticaria and cholinergic urticaria are not uncommonly seen together; and cold-induced cholinergic urticaria represents an unusual variant in which typical “cholinergic”-appearing lesions occur with exercise, but only if the person is chilled, for example, with exercise outside on a winter's day. The ice cube test and methacholine skin test both yield negative results.