Abstract:We report the singular association of mediastinal pseudo-tumoral tuberculosis [TB] with systemic lupus erythematosus [SLE]. D. I, 22 years old woman, is followed for a SLE since 2006 controlled by hydrochloroquine 'HCQ'200mg twice/day and a thyroiditis of Hashimoto under levothyrox 125 mg/d. It does not relate to tuberculosis. She is hospitalized in pneumology for progressive dyspnea and chest pain. Objective clinical examination shows a conserved general condition, apyrexia T° to 37, BMI to 21.1 (without notion of loss of weight), heart beat 94 / min, respiratory rate at 24 cycle/min and blood pressure at 110/60 mmHg. The pleuropulmonary and cardiovascular examination were without abnormality and thus the remainder of the clinical examination. The image of the thoracic face fails with a right para-cardiac opacity erasing the right edge of the cortex and the CT concludes to a mediastinal tumoral process, filling the gutter vertebral and extending from T6 to T10, with tissue density presenting areas of necrosis within it. Bronchial fibroscopy finds a thickening of inter-lobar spurs and bronchial biopsies identifies a bronchial mucosa site of chronic inflammatory remodeling with presence of multi-nucleated giant cells suggesting a tuberculoid process. The parameters of the hemogram were normal and the inflammatory syndrome was attested by both the increase ERS at 54 mm and the level of CRP at 12 mg/l. The smears, negative on direct examination, will prove positive for culture on Lowenstein medium. Antituberculosis treatment has been prescribed with good clinical, bacteriological and radiological progress. Long-term asymptomatic mediastinal pseudo-tumoral tuberculosis can be revealed at the compressive stage by dyspnea and chest pain. The fear of lymphoma requires biopsies with pathological examinations which sometimes reveal benign affections (tuberculosis, sarcoidosis in their tumor forms) which can enamel the autoimmune disorders characterizing a SLE.