[Pleural effusion of non-neoplastic etiology in a patient with a rare form of myeloma].

Pleural effusions can be a manifestation of several nosological entities. Etiologic diagnosis involves a good clinical history, followed by thoracocentesis with pleural biopsy and eventually bronchoscopy or thoracoscopy. The differentiation between transudates and exudates, by the biochemical characteristics of the pleural effusions, can orientate the underlying disorder. It is known that there are more than 35 different etiological entities of exudative pleural effusions. However, pneumonia, malignancies, pulmonary embolism, abdominal disease and tuberculosis are the major causes (around 90%). Transudative effusions are more frequently due to congestive heart failure, renal or hepatic failure. The AA present a clinical situation of pleural effusion, the etiology of which was initially attributed to congestive heart failure, with a good response, clinical and radiological response to the treatment established. However the laboratory alteration persisted (anaemia, renal failure, acute inflammation). The subsequent study showed the existence of a rare syndrome, a Myeloma Ig M lambda that can lead to differential diagnosis with Waldenström's Macroglobulinemia, about which the authors make some theoretical considerations showing the difficulty in etiologic diagnosis of some pleural effusions.