Abstract: Objective  To compare the clinical data of secondary pulmonary tuberculosis  and adult mycoplasmal pneumonia and to lay foundation for the differential diagnosis for the 2 diseases.  Methods  Sixty-seven cases and 32 cases of the 2 diseases were collected in our hospital from 2008 to 2010, and the clinical performance, X-ray information, laboratory examination and therapy of the patients were retrospectively analyzed.   Results  （1）The course of most adult mycoplasmal pneumonia patients was usually shoter（87.5%，28/32）than secondary pulmonary tuberculosis patients（7.5%，5/67）（χ²=62.3898，P<0.01）, and symptoms of respiration［runny nose（68.8%，22/32），headache（28.1%，9/32），sore throat（50.0%，16/32）］ were more common than those of patients with secondary pulmonary tuberculosis（3.0%（2/67），6.0%（4/67）,4.5%（3/67））（χ²=51.1830，χ²=9.2565，χ²=30.8682，All P<0.01）. The sign of rale was found more in mycoplasmal pneumonia patients （53.1%，17/32）than that in secondary pulmonary tuberculosis patients（13.4%，9/67）（χ²=17.6145，P<0.01）. （2）The most common CT finding of adult mycoplasmal pneumonia were ground glass opacity and consolidation（71.9%，23/32），with none of secondary pulmonary tuberculosis patients（χ²=62.7398，P<0.01）.Most of the ground glass opacity and consolidation showed tendency of lobular distribution and involving the lower lobes（70.0%，14/20）in patients with mycoplasmal pneumonia, while secondary pulmonary tuberculosis patients was 34.2%（13/38）（χ²=9.5139，P<0.01）. In some patients with mycoplasmal pneumonia, the focus was wandering（9.4%，3/32）, while secondary pulmonary tuberculosis patients was not found （χ²=5.9103，P<0.05）.The lesions was absorbed after treatment with azithromycin or erythrocin in 4 weeks（53.1%，17/32）in mycoplasmal pneumonia, but that could not be seen in secondary pulmonary tuberculosis patients （χ²=42.8718，P<0.01）. （3）Serum cold agglutination test and  antibody of mycoplasma pneumoniae were different between adult mycoplasma  pneumonia secondary pulmonary tuberculosis（71.9%（23/32） vs. 0，χ²=62.8571，P<0.01; 81.3%（26/32）vs 1.5%（1/67），χ²=67.5228，P<0.01）.  Conclusion  It is helpful to identify the diagnosis between secondary pulmonary tuberculosis and adult mycoplasma  pneumonia if taking medical history carefully, noticing focus characters on imaging, given empirical treatment and multiple serology and bacteriology examination.

Key words: Tuberculosis,pulmonary/diagnosis, Pneumonis,mycoplasma, Diagnosis,differential