Mycobacterium smegmatis causing a granulomatous cardiomediastinal mass

Non-tuberculous mycobacterial species are uncommon human pathogens. They are divided into slow and rapid growing mycobacteria (RGM) with Mycobacterium smegmatis group as an uncommon pathogen among the RGM.A 19 years old male presented with a 1 month history of dyspnea, orthopnea, unintentional weight loss, palpitation, flu-like symptoms and dry cough. Physical examination revealed tachycardia, distended superficial chest veins with a decrease in breath sounds at the right lower lung with fine crepitations. CT of the chest showed a large anterior mediastinal mass infiltrating the pericardium and three chambers of the myocardium that was confirmed using echocardiography. Despite negative workup for tuberculosis, the patient was treated successfully using first-line anti-TB treatment, which was begun before the tissue culture grew M. smegmatis.To our knowledge, this is the first case in the literature of M. smegmatis infection mimicking cardiomediastinal tuberculoma, and RGM should be suspected in similar presentations with negative TB workup, even in an immunocompetent patient. This is also the first patient to be treated using only first-line anti-tuberculous treatment successfully in the literature. Keywords: Mycobacterium smegmatis, Cardiac, Granuloma, Saudi Arabi

Lung granuloma: A clinicopathologic study of 158 cases

Background and Aims: A granuloma is a common pathological diagnosis in lung biopsies and is caused by a variety of etiologies. The aim of this study was to assess the etiology and frequency of different cases of lung granulomas. Methods: The medical records of all patients who had lung granulomas between 2005 and 2013 were retrospectively reviewed. Based on the histological features of the granulomas, along with the clinical, laboratory, and radiological findings, an attempt was made to identify the etiology of the granuloma in each case. Results: A total of 158 patients with lung biopsy specimens showing lung granulomas were identified. The histological findings revealed necrotizing granulomas in 92 (58%) of the cases and nonnecrotizing granulomas in 66 (42%). A definite etiology was determined in 133 cases (84%), whereas in 26 cases (16%), the etiology could not be identified despite an extensive workup. Infection was the most frequent cause of granuloma, accounting for 105 cases (66%). Mycobacterial tuberculosis (TB) was the type of infection that caused the largest number of granulomas, and was responsible for 100 cases (63%). Among the noninfectious etiologies of lung granuloma, sarcoidosis was the most common cause, accounting for 20 (13%) of the cases. Conclusions: Mycobacterial TB and sarcoidosis are the most common causes of lung granulomas in our region. In a substantial proportion of cases, the cause may not be identified despite an extensive workup