Legionnaire's disease with limbic encephalitis

Legionnaires' disease is a severe primary pneumonia and is recognized as a major form of community-acquired pneumonias caused by Gram-negative bacteria, Legionella species which are globally ubiquitous, intracellular and freshwater bacteria. Cigarette smoking, chronic lung disease, alcohol, dialysis, immunosuppression and surgery have been consistently implicated as risk factors. The severity of legionellosis varies, and it can manifest as a potentially fatal form of pneumonia that can also occur in individuals with immune competence. Extra-pulmonary manifestations, including neurological symptoms are frequent, and the complications of transient lesions in the corpus callosum, as demonstrated by magnetic resonance imaging, are well known in Legionnaires' disease. Furthermore, there have been cases in which impaired mental have appeared before the onset of pneumonia. We herein present the case of a 52-year-old man with limbic encephalitis and Legionella pneumonia. The urinary antigen test for Legionella was positive. Legionella species were not detected in cerebrospinal fluid cultures using Wadowsky-Yee-Okuda agar. Furthermore, a sputum culture was negative, and Legionella species were not detected by a sputum molecular test using the Loop-mediated Isothermal Amplification method. Although both his pneumonia and brain magnetic resonance imaging abnormalities resolved, his short-term memory impairment remained. This case illustrates an exceptionally rare combination of Legionnaires' disease and limbic encephalitis, with few comparably detailed reports available.