1. Mycoplasmal pneumonia Pneumonia caused by Mycoplasma pneumoniae, often accompanied by pharyngitis and bronchitis

2. Epidemiology the smallest free-living organisms, facultative anaerobes no cell wall accounts for 10 to 20% of all pneumonias and for at least half of all pneumonias in children and young adults typically community-acquired, spread person to person via droplet nuclei after close and prolonged contact not seen on Gram stain cannot be treated with the β- lactams or vancomycin

3. Clinical findings most patients are older children, adolescents, and young adults 75% of patients tracheobronchitis, 5% atypical pneumonia, and 20% asymtomatic protracted coughing results in tracheal tenderness and a sore chest t he insidious onset is followed by gradual recovery. Upper respiratory symptoms may last for 2 to 3 weeks, and signs of pneumonia may persist for 4 to 6 weeks

4. Sequence of symptoms begins insidiously over days or a week with constitutional symptomatology (e.g., fever, myalgia, headache, and malaise) then upper respiratory signs and symptoms appear, with combinations of sore throat, cervical adenopathy, hoarseness, earache, coryza, and non-productive cough less commonly, croup or bronchiolitis may supervene, and in a small percentage, pneumonia ensues, at this point, the cough becomes productive

5. Signs: fever, an erythematous pharynx without exudate Laboratory findings: a slight leukocytosis with normal differential count Radiographic findings: manifold. Most patients have unilateral lower lobe segmental abnormalities on the right

6. Diagnosis Mycoplasma culture (1) not widely available (2) recovery of the organism from sputum does not prove the diagnosis because it can persist for a long time after infection ( >4 weeks)

7. Serologic diagnosis: complement fixation test (CFT) or ELISA 90% of patients either a four-fold rise in antibody titer (2 to 3 weeks apart) or a single titer of 1:32 or greater Problems: 1. CFT titer remain elevated for a year after infection 2. the glycolipid antigen in CFT not specific for Mycoplasma, also in: human heart muscle, brain, and pancreas, some streptococci and leafy vegetables false-positive 3. false-negative reactions are seen with both tests 4. antibody appears only after 7 to 10 days of illness 5. detection of IgM does not prove current infection but indicate a recent infection (IgM may persist for months)

8. Antigen detection (direct detection): DNA probes, PCR Limited in view of prolonged carrier state The diagnosis is proved by a four-fold rise in antibody titer strongly supported by a single antibody titer of 1:32 or greater, a titer of cold agglutinins of 1:64 or greater, or a single IgM determination

9. Differential diagnosis Psittacosis contact with birds. Q fever exposure to farm animals or cats. Legionella infect older men who smoke. Chlamydia pneumoniae causes a biphasic illness, with sore throat and hoarseness followed by cough. True viruses cause a more fulminant pneumonia Factors suggesting a mycoplasmal etiology sore throat, headache, fever, rash, an indolent course, a paucity of physical findings on examination, and a chest radiograph more abnormal than the physical examination predicted

10. Therapy Empirical culture takes time and may be misleading serologic investigation not diagnostic early in the course Standard therapy: erythromycin or tetracycline (2g daily in divided doses) doxycycline, the newer macrolides (azithromycin and clarithromycin) & FQNS can substitute

11. Duration of therapy most recommendations are for 10 to 14 days of therapy longer courses of treatment (e.g. 2 to 3 weeks ) may avoid the relapse that occurs in 5 to 10% of patients