Cause:Legionella pneumophilia,etc
Airborne or drinking water-borne (Nejm 1992;326:151)
Epidemic and endemic. Male > female; summer/fall peaks; many unrecognized cases; 5% of all community-acquired pneumonias; spread by air conditioner systems (Nejm 1980;302:365). Increased incidence in patients on dialysis, with DM, COPD, over age 50 yr, on chemotherapy
Sx:2- to 10-d incubation. *Diarrhea (2/3); cough without sputum, pleurisy, headache, recurrent rigors; r/o mycoplasma and psittacosis
Si:*Pneumonitis, *fever, slow pulse, confusion, wound infections (UVM—Ann IM 1982;96:173)
*Most important findings for dx.
r/o other atypical pneumonia agents, eg, Pittsburgh agent and very similar PONTIAC FEVER(Ann IM 1984;100:333)
Lab:
Bact:Sputum Gram stain shows polys without bugs; gram-neg rod when pick culture, won't stain in tissue. Fluorescent antibody stains of transtracheal aspirate or sputum, pos in 26%. Culture requires special media, very fastidious
Chem:LFTs increased (1/2); Na <130 (2/3)
Hem:ESR increased (1/3); polys increased (2/3) with left shift
Serol:Titer >1/250 IgG and IgM
Urine:3+ protein (20%), rbc's. Urine antigen by RIA or ELISA, 70% sens, 100% specif; is the clinically most useful test
Xray:Chest shows bilat pneumonia, 1/3 w pleural effusion
Rx:
(Nejm 1998;129:328)
Azithromycin, clarithromycin, or erythromycin × 10-14 d; ciprofloxacin 400 mg iv q 8 h or 750 mg po bid, or newer fluoroquinolone; doxycycline, but less effective. Add rifampin in severe disease