The following is a sample question and explanation from the ABFM that explains the presentation of Legionella Pneumophilla
“Legionella should be considered as a pathogen for community-acquired pneumonia when the patient has a history of a hotel stay or cruise ship travel within the past couple of weeks. ”
“A previously healthy 74-year-old male presents to the emergency department with a fever and altered mental status. His illness began 2 days ago with symptoms of fever, malaise, body aches, reduced appetite, nausea, and diarrhea. His temperature is 39.6°C (103.3°F) in the emergency department and his examination is nonfocal. Initial laboratory studies include a sodium level of 131 mEq/L (N 135–145) and a WBC count of 14,200/mm3 (N 4500–11,000) with a neutrophilic predominance. Blood and urine cultures are obtained and he is admitted to the hospital for observation. The next morning he develops a productive cough and shortness of breath. You order a chest radiograph, which shows patchy consolidation of the bilateral bases. Which one of the following is the most likely cause of this patient’s condition?
Answer: Legionella pneumophila
Rationale:
Pneumonia caused by Legionella pneumophila is commonly preceded by nonspecific systemic symptoms that may lead a clinician to consider other diagnoses. Symptoms may include high-grade fever, malaise, myalgias, anorexia, and headache. Gastrointestinal and neurologic symptoms are also common and include nausea, vomiting, abdominal pain, diarrhea, and confusion. Focal neurologic signs are less common, but have been reported. Localizing respiratory symptoms will typically develop later, most often a dry cough and dyspnea. From this point on the illness resembles atypical pneumonia with fever, productive cough, pleuritic pain, and breathlessness.”
Darby J, Buising K: Could it be Legionella? Aust Fam Physician2008;37(10):812-815.