[Superior vena cava syndrome and Riedel's thyroiditis. Report of a case: review of the literature].

The authors present the case of a 42-year-old female patient, initially admitted to hospital for the etiological diagnosis--which remained negative--and the treatment of a superior vena cava syndrome. This patient was seen again two years later as the superior vena cava syndrome recurred, while a thyroid syndrome appeared at the same time. Exeresis followed by a clinicopathological study demonstrated Riedel's chronic fibrous thyroiditis. The authors study the causal relationships between both conditions and their integration into multifocal fibroses. To their knowledge, this is the first case in which the superior vena caval syndrome is the site of occurrence of fibrosis, precedes the thyroid involvement. The new radiological technique at our disposal--CT, MRI--should allow more easily searching for the various sites of the fibrosing disease (biliary ducts, pancreas, duodenum, retroperitoneum, mediastinum, orbits), and immunological studies will make it possible to better classify them and define their pathogenesis.