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Legionnaire's diseaseLegionella pneumonia Infectious disease A lung infection caused by Legionella pneumophila, which is either sporadic or epidemic with a mortality of up to 15%; depending on the population, Legionella spp cause 1–27% of CAPs; ♂:♀ ratio, 3:1 Epidemiology Most
L pneumophila infections are associated with buildings and ventilation systems; most epidemics occur during the summer with 0.5 to 5% attack rates; the only documented mode of spead is by air Risk factors Cigarettes, alcohol, renal transplant, ↑ age Clinical 2-10 day incubation, followed by an abrupt malaise, headache, myalgia, a dry, initially non-productive, later productive, cough, hemoptysis; fever to 40ºC, rigors often associated with bradycardia; less commonly, nausea, diarrhea, delirium, septicemia, abscesses, acute myocarditis, pericarditis, rhabdomyolysis DiffDx Sporadic LD mimics myoplasma pneumonia, Q fever, tularemia, plague, psittacosis, influenza and other viral pneumonias CXR Patchy, segmental, or lobar, often bilateral, alveolar infiltrates, often progressing to nodule Lab ↓ Na+, ↓ PO4–, ↑ liver enzymes, proteinuria, microscopic hematuria, relative leukocytosis, ↑ ESR, hyponatremia, ↑ ALT,
↑ AST, ↑ BR, azotemia Complications Empyema, shock, DIC, renal failure, neurologic sequelae, peripheral neuropathy Management Erythromycin, T-S, penicillin Prognosis 15-20% death w/o therapy; up to 50% death in immunocompromised Pts Poor prognostic features Tachycardia, tachypnea, WBCs
≥ 14,000/mm3, ↑ BUN, ↑ creatinine, hyponatremia, hypoxia, leukopenia, bilateral infiltrates on CXR Prevention Chlorination; UV irradiation of water supplies. See Community-acquired pneumonia, Legionella pneumophila. Cf Pontiac disease.
A lung disease caused by a bacterium.
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