Unusual cold-induced disorders: cold-dependent dermatographism and systemic cold urticaria.

Two patients are described in whom new cold-induced disorders were defined. The patients presented with histories suggesting either dermatographism or typical cold urticaria; however, standard tests for each disorder failed to reproduce the patients' symptoms. One patient had dermatographism that was observable only upon chilling the skin subsequent to scratching it. The reaction was associated with detectable elevation of venous histamine levels coincident with the development of urticaria. The second patient had generalized urticaria that was induced by systemic rather than local cold challenge. The reaction was anaphylactoid in nature and was associated with systemic elevation of histamine levels. This patient was also mildly dermatographic, and skin reactivity was markedly augmented during an episode of generalized hives. These cold-dependent disorders should be included in the differential diagnosis of patients with histories suggestive of cold urticaria with or without a dermatographic component. Further evaluation is indicated when the standard tests for either of these disorders are negative.