Case Presentation: A 58-year-old man with history of heavy tobacco use, presented to the emergency department with intermittent watery nonbloody diarrhea for 4 days, associated with worsening confusion and decreased urine output. He denied recent traveling or sick contacts. On examination he was found to be febrile (102.6F), hypertensive, tachycardic (102bpm) and tachypneic (22rpm) and oxygen saturation of 95% on room air. He had diminished breath sounds over his right lower lung field and was not oriented to time. Laboratory evaluation was notable for mild hyponatremia (133mEq/L), acute renal failure (ARF) with creatinine of 8.6mg/dL and blood urea nitrogen of 92mg/dL, and mild transaminitis (alanine aminotransferase 111unit/L and aspartate transaminase 214unit/L). Leukocytosis was not present. Creatinine kinase was markedly raised up to 8,170unit/L and urine analysis showed 3+ blood without significant red blood cells. Chest x-ray revealed an opacification of the central portion of his right lung, consistent with a lobar pneumonia. Legionella urine antigen was performed, which came positive. He was promptly started on intravenous fluids and levofloxacin monotherapy, after which his symptoms and laboratory abnormalities resolved. Patient was discharged to complete 10 days of antibiotic therapy.

Discussion: Legionnaire’s disease (LD) is an important cause of nosocomial and community-acquired pneumonia, with 2-15% of these cases requiring hospitalization. LD can cause multiple organ failure and death in 10% of treated immunocompetent patients, with progressive respiratory failure been the most common cause of death. Less commonly, LD can cause rhabdomyolysis resulting in acute renal failure, which raises the mortality if not recognized early. The overall mortality due to LD is 5–15%, however, when rhabdomyolysis and renal failure are present, this can increase up to 40%. While the mechanism of rhabdomyolysis associated with Legionella is unknown, theories include direct invasion of Legionella into the muscle itself, or the release of endotoxins into the circulation, with subsequent muscle injury. With treatment, renal function usually recovers; nevertheless, in severe cases, patients may require renal replacement therapy.  Overall prognosis of LD is based on the early administration of an appropriate antibiotic treatment and patient’s comorbidities including old age, chronic smoking, associated immunodeficiencies, among others.

Conclusions: Legionella must be considered as a potential pathogen in any patient who presents with atypical pneumonia. Associated rhabdomyolysis is an important complication we need to identify and treat opportunely. Outcomes may be fatal if prompt antibiotic therapy is delayed.