bubble_chart Overview

It is a lung infection caused by Legionella pneumophila (a Gram-negative bacillus). The mild form presents only flu-like symptoms, while the severe form develops into pneumonia, often accompanied by extrapulmonary symptoms, also known as Legionnaires' disease.

bubble_chart Diagnosis

1. Medical History and Symptoms:

1. Common predisposing factors include smoking, alcohol abuse, and immunosuppression. 2. Prodromal symptoms include lack of strength, drowsiness, fever, headache, and myalgia. 3. Respiratory symptoms include cough, sputum production (mucoid, purulent, or bloody sputum), chest pain, and dyspnea. 4. Extrapulmonary symptoms: nausea, vomiting, diarrhea (loose or watery stools), drowsiness, confusion, delirious speech, unconsciousness, dementia, anxiety, convulsions, disorientation, depression, hallucinations, insomnia, forgetfulness, speech disorders, and abnormal mental status.

2. Physical Examination Findings:

Acute Rebing appearance, relatively moderate pulse, possible hypotension, tachypnea, superficial lymphadenopathy, hepatosplenomegaly, moist rales may be heard in the affected lungs, and there may be signs of a small amount of pleural effusion. Signs of extrapulmonary involvement may appear when combined with extrapulmonary lesions.

3. Auxiliary Examinations:

(1) Chest X-ray: lacks specificity, early stage shows patchy shadows on one or both sides, late stage [third stage] shows inflammatory infiltration, more common in the lower lungs, abscesses and cavities are only seen in immunocompromised patients, and pleural effusion may be present.

(2) Etiological examination: 1. Diagnosis can be confirmed by culturing Legionella from sputum, blood, or pleural fluid. 2. Bacterial antigen and DNA detection can be performed using direct fluorescent antibody (DFA), enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), gene probes, and polymerase chain reaction (PCR). 3. Serum-specific antibody detection: includes indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), microcontamination test, and tube agglutination test (TAL).

(3) Other examinations: White blood cell count is mostly normal or slightly increased, some show a left shift in neutrophil nuclei, and those with decreased white blood cells have a poor prognosis. There may be hematuria, increased aspartate aminotransferase and lactate dehydrogenase, jaundice, and hypocupremia and hypomagnesemia.

(4) Differential diagnosis: Should be differentiated from pneumonia caused by other pathogens.

bubble_chart Treatment Measures

1. Antibiotic Treatment:

Erythromycin is the first choice. For mild cases, take 0.5g orally every 6 hours; for severe cases, administer 1.5-2g/day intravenously. Alternatively, use new penicillin 0.5g four times a day for 4 days; or clarithromycin 0.25g every 12 hours, then 0.2g once a day, or 0.1g twice a day. The treatment course is 7-14 days. For immunocompromised or severely ill patients, ofloxacin 0.4g every 12 hours, or ciprofloxacin 0.5g every 12 hours orally or 0.4g every 12 hours intravenously. For antibiotic use, immunocompromised patients should be treated for no less than 3 weeks, and for those with lung abscess, the treatment should be extended to 3-4 weeks.

2. Rifampin:

For the first 3-5 days, take 0.6g twice a day, or use in combination with erythromycin and compound formula sulfamethoxazole-trimethoprim (SMZ-TMP) for good efficacy.

3. Symptomatic Treatment:

Provide cough suppressants, phlegm-resolving drugs, etc. For hypotension and respiratory failure, provide oxygen and respiratory support. Discontinue or reduce the dose of immunosuppressants if previously used. For adrenal insufficiency, use hormones if necessary.