Updated: 12/19/2019

Legionnaires Disease

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  • A 75-year-old woman returns from a week-long cruise with a cough and sputum production. Her family notices that she seems more confused than usual and brings her into the hospital. Earlier today, she had complained of nausea and vomiting. On physical exam, her pulse is 60/min. There are fine crackles diffusely on chest auscultation. Laboratory tests show that she has hyponatremia and mildly elevated transaminitis. A urine antigen test is positive for the suspected disease and she is started on antibiotics.
  • Classification
    • Legionella pneumophila
      • an aerobic, facultative, intracellular gram - rod
    • transmission
      • aspiration of contaminated water/soil
        • air conditioning
        • hot tubs
        • swimming pools
  • Epidemiology
    • demographics
      • more common in the elderly
    • risk factors
      • cruise ships
      • smoking
      • immunosuppression
      • hospitalization
  • Pathogenesis
    • organism is phagocytosed into alveolar macrophages, where they replicate
    • bacterial spread occurs when they escape from macrophage vacuoles leading to host cell osmotic lysis
  • Associated conditions
    • Legionnaires disease (most common)
      • lobar or insterstitial pneumonia
      • gastrointestinal and central nervous system involvement
      • more common in smokers and those with chronic lung diseases
  • Symptoms
    • cough with sputum production
    • gastrointestinal symptoms
    • nausea or vomiting
    • water diarrhea
    • central nervous system symptoms
      • confusion
      • encephalopathy
  • Physical exam 
    • fever
    • altered mental status
    • dyspnea
    • relative bradycardia
    • pneumonia
  • Chest radiography
    • indication
      • all patients
    • findings
      • lobar consolidation or
      • diffuse patchy infiltrates
  • Labs
    • urine antigen test 
      • diagnostic
    • does not Gram stain well, so this requires a silver stain
    • sputum culture
      • requires special media for culture
      • charcoal yeast extract agar buffered with iron and cysteine 
    • hyponatremia
    • transaminitis
  • Making the diagnosis
    • based on clinical presentation and laboratory studies
  • Mycoplasma pneumoniae
    • distinguishing factor
      • typically does not present with gastrointestinal or central nervous system involvement
  • Medical
    • antibiotics
      • indication
        • all patients
      • drugs
        • macrolides
        • respiratory fluoroquinolones (levofloxacin and moxifloxacin)
  •  Respiratory failure

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Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2

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(M2.ID.17.4765) A 38-year-old female presents to the emergency department for cough. She reports that two days ago she developed a nonproductive cough with moderate shortness of breath. On review of systems, the patient also endorses chills and sweats as well as several episodes of diarrhea over the past three days. Her husband also reports that the patient seemed confused this morning when he spoke to her before he left for work. The patient’s past medical history is significant for diabetes mellitus type II for which she takes metformin and glipizide. She drinks 8-10 beers per week and has a 15 pack-year smoking history. She works as a sales manager at a local retail company. Her temperature is 102.6°F (39.2°C), blood pressure is 126/72 mmHg, pulse is 82/min, and respirations are 18/min. On physical exam, she is alert and oriented to person and place only. She has crackles bilaterally extending up to the mid-lung fields. Her abdomen is soft and non-distended without rebound or guarding. Laboratory testing is performed and reveals the following:

Na+: 129 mEq/L
K+: 3.6 mEq/L
Cl-: 99 mEq/L
HCO3-: 17 mEq/L
Urea nitrogen: 16 mg/dL
Creatinine: 1.1 mg/dL

Leukocyte count: 16,300/mm^3
Hemoglobin: 13.2 g/dL
Mean corpuscular volume: 87 µm^3
Platelet count: 348,000/mm^3

A chest radiograph is performed and can be seen in Figure A. Which of the following is most likely to be elicited upon further questioning?
Review Topic | Tested Concept

QID: 109039

Risk factors for aspiration




Recent travel to Arizona




Exposure to incarcerated population




Recent cruise travel




Exposure to bird droppings



L 2 D

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