Exanthema in Legionnaires' disease mimicking a severe cutaneous drug reaction.

Legionnaires' disease is an acute bacterial infection, generally caused by Legionella pneumophila, which primarily involves the lower respiratory tract, although it is often associated with multisystemic extrapulmonary features. Cutaneous features are very uncommon and may include erythematous or petechial, macular or maculopapular lesions. We report a male patient who expressed all features of a severe lobular pneumonia. Over the course of the disease the patient developed a livid erythematous, maculopapular exanthem rapidly extending over the entire body. Given the rapid development and target-like appearance of the skin lesions with extensive skin involvement and blister formation, the initial diagnosis was that of a severe cutaneous drug reaction. However, histological examination of biopsy did not confirm this diagnosis, but instead was suspicious for a viral exanthem or a more aggressive inflammatory response due to sensitization to bacterial antigens. L. pneumophila infection was verified during the course of the disease.