We report here a critically ill patient with renal-lung syndrome and multiple organ failure who was admitted at our Critical Care Service 40 days after onset. The clinical and biological findings suggested an immunological disorder like a systemic lupus eritematosus (SLE) inmmediate battery of immunological tests was carried out with metilprednisolane therapy and vital support measures. We confirm a SLE by serology after the patient died six days later. prompt diagnosis and treatment of these disorders may be life-preserving but the diagnosis may be complicated by the vagaries of serologic testing and the understandable hesitancy in utilizing invasive procedures, including open or thoracoscopic lung biopsy, fibrobronchoscopy with transbronchial biopsy and lavage in these critically ill patients