[Four cases of pulmonary infection due to Mycobacterium szulgai with a review of previous case reports in Japan]

We report 4 cases of pulmonary infection due to Mycobacterium szulgai with review of 23 cases previously reported in Japan. All 4 patients were male and two of them in their 20's were found to have abnormal chest X-ray findings recognized on a health checkup without any symptoms. One case had no previous history of illness and had never smoked. Radiographic study showed thick-walled cavities in 3 cases and multiple small nodules in 2, indicating the difficulty of distinguishing M. szulgai infection from pulmonary tuberculosis or M. kansasii infection. Three cases were treated as pulmonary tuberculosis at first, and later we changed the medication referring to the drug susceptibility. In most cases, rifampicin, ethionamide and ethanbutol were used and the medication regimen was successfully completed in all cases. Considering that the detected M. szulgai could be regarded as pathogen in almost all cases, it is important to evaluate the risk factor of patients and not to delay diagnosis and treatment with adhering to usual diagnostic criteria.