A 56-year-old woman is brought to the emergency department due to a 2-day history of high fever, headache, mild confusion, and dry cough. She also has mild abdominal discomfort and watery diarrhea. The patient recently returned from a cruise to Hawaii. Her other medical problems include hypertension and hyperlipidemia. She has smoked 1 pack of cigarettes daily for over 20 years. Her temperature is 40 C (104 F), blood pressure is 104/63 mm Hg, pulse is 85/min, and respirations are 24/min. Lung examination reveals lower lobe crackles with no wheezing. Her abdomen is soft, non-distended, and non-tender. Chest x-ray shows bilateral lower lobe interstitial infiltrates. Which of the following additional findings is most likely to be present in this patient?

Question

A 56-year-old woman is brought to the emergency department due to a 2-day history of high fever, headache, mild confusion, and dry cough.  She also has mild abdominal discomfort and watery diarrhea.  The patient recently returned from a cruise to Hawaii.  Her other medical problems include hypertension and hyperlipidemia.  She has smoked 1 pack of cigarettes daily for over 20 years.  Her temperature is 40 C (104 F), blood pressure is 104/63 mm Hg, pulse is 85/min, and respirations are 24/min.  Lung examination reveals lower lobe crackles with no wheezing.  Her abdomen is soft, non-distended, and non-tender.  Chest x-ray shows bilateral lower lobe interstitial infiltrates.  Which of the following additional findings is most likely to be present in this patient?

Quizplus · Accepted Answer

11ec160b_3898_9e74_9249_5b350c14b2d0_MD0001_00 Legionellosis can be divided into Pontiac fever (an acute, flu-like, self-limited disease) and the more common Legionnaires' disease. Legionnaires' disease should be suspected in patients with recent exposure to contaminated water (sporadic cases or common-source outbreaks in cruise ships, spas, hospitals, or air-conditioned hotels), radiographic evidence of pneumonia (typically patchy infiltrates that may progress to consolidation), high fever (>39 C [102.2 F]) sometimes associated with relative bradycardia, neurologic symptoms (eg, confusion, headache), and gastrointestinal (GI) symptoms (eg, diarrhea). Risk groups include the elderly or immunocompromised, smokers, and patients with chronic obstructive pulmonary disease. Because Legionella pneumophila is a faintly staining gram-negative bacillus that is facultatively intracellular, Gram stain typically shows many neutrophils but few or no organisms. Legionella is often diagnosed by urinary antigen testing; it grows on selective medium (buffered charcoal yeast extract [BCYE]). The most common laboratory abnormality is hyponatremia, frequently associated with Legionella but not other causes of pneumonia. The hyponatremia may be related to inappropriate antidiuretic hormone secretion and/or renal tubulointerstitial disease impairing sodium reabsorption (possibly due to either direct effect of Legionella, cytokines, or natriuretic peptides). Elevated transaminases are also common. (Choice A) This patient does not have asthma, making allergic bronchopulmonary aspergillosis (pulmonary infiltrates/bronchiectasis with eosinophilia and elevated IgE and anti-Aspergillus antibody titers) unlikely. Some helminthic infections are associated with pulmonary infiltrates and eosinophilia (Löffler). However, high fever, neurologic symptoms, and concurrent GI and pulmonary symptoms are unusual. (Choices B and D) Streptococcus pneumoniae (gram-positive diplococci on Gram stain) is the most common overall cause of community-acquired pneumonia. Lobar consolidation is classic. Patients with influenza A typically experience the abrupt onset of fever, headache, myalgias, and malaise that gradually improve over 2-5 days, with a subset developing secondary bacterial pneumonia (exacerbation of fever and respiratory symptoms after initial improvement). However, dry cough, GI and neurologic symptoms, and interstitial infiltrates in the setting of a recent cruise make Legionella more likely. (Choice E) Mycoplasma pneumoniae infection can result in cold agglutinin formation. However, M pneumoniae predominantly affects young adults and is more likely to cause tracheobronchitis than pneumonia. Clinical presentation is typically mild with bilateral infiltrates on chest x-ray appearing more severe than expected based on clinical findings. Educational objective: Legionella pneumophila is a facultative intracellular gram-negative bacillus that can cause a systemic infection. Symptoms frequently include high fever, cough, confusion, and diarrhea. The most common laboratory abnormality seen with Legionella pneumonia is hyponatremia, and sputum Gram stain often shows many neutrophils but few or no organisms. __________ References: Could it be Legionella? (http://www.ncbi.nlm.nih.gov/pubmed/19002299)

A 56-Year-Old Woman Is Brought to the Emergency Department Due