Síndrome de Caplan: la paradoja del pulmón como origen de la artritis reumatoide / Caplan syndrome: the paradox of the lung as the origin of rheumatoid arthritis

Resumen Históricamente, los estudios de campo observacionales han sido el punto de partida para el desarrollo de grandes avances en el entendimiento de las enfermedades autoinmunes. En el caso de la artritis reumatoide (AR), se han descrito varias asociaciones clínicas hasta la actualidad que tienen en común modelos inmunológicos transversales a la historia natural de la misma, lo que ha permitido avanzar en el desarrollo de nuevos objetivos terapéuticos. Se pretende hacer una breve descripción del compromiso nodular en AR, partiendo de las observaciones clínicas del Dr. Anthony Caplan en pacientes con riesgo de neumoconiosis, con el fin de reconocer el valor de este tipo de asociaciones en el ejercicio médico profesional.

Historically, observational field studies have been the starting point for the development of great advances in the understanding of autoimmune diseases. In the case of rheumatoid arthritis (RA), several clinical associations have been described to date which have in common immunological models transverse to its natural history, which has allowed progress in the development of new therapeutic objectives. Our aim is to make a brief description of nodular involvement in RA, based on the clinical observations of Dr. Anthony Caplan in patients at risk of pneumoconiosis, in order to recognize the value of this type of association in professional medical practice.

Rheumatoid pneumoconiosis (Caplan's syndrome).

In 1953, Caplan described a characteristic radiographic pattern in coal miners with rheumatoid arthritis (RA) that was distinct from the typical progressive massive fibrosis pattern of coalworkers' pneumoconiosis. It consists of multiple well-defined rounded nodules on chest X-ray, from about 0.5 to about several centimetres in diameter, distributed throughout the lungs but predominantly at the lung periphery. Lesions appear often in crops, may coalesce and form a larger confluent nodule. Nodules often cavitate or calcify. They typically occur in the setting of pre-existing mild pneumoconiosis, but pneumoconiosis is not a prerequisite. The onset of the nodules is typically sudden, and their course varies thereafter, ranging from regression to progression. Histologically, the nodules have a characteristic appearance and are distinguishable from silicotic nodules or progressive massive fibrosis. Individual susceptibility is considered to play a role in the development of the disease. However, the pathogenetic link between exposure to silica, pneumoconiosis and RA has not been clarified conclusively. This review summarizes history, definition and current knowledge on epidemiology, pathology, pathophysiology, clinical presentation and treatment of Caplan's syndrome.

[Biventricular inflow tract compression by chronic organized hemopericardium in Caplan syndrome]. / Biventrikuläre Einflusstraktkompression durch chronisch organisiertes Hämoperikard bei Caplan-Syndrom.

We report the case of a 59-year old patient with the rare combination of silicosis and rheumatoid arthritis, which is called Caplan's syndrome. The patient presented with right heart failure caused by a pericardial tumor compressing the right and the left ventricle. By means of several imaging techniques it was possible to elucidate the topographic relations of the tumor. Definite signs of malignant growth were not found. Despite his elevated perioperative risk we decided to operate on the patient. During the operation macroscopic and histologic evidence revealed that the tumor was not a neoplastic process but consisted of an organized hemopericardium. This demonstrates that pericarditis in rheumatoid arthritis can be hemorrhagic and can mimick a malignant pericardial tumor. The decision to operate was first supported by the findings of the applied imaging techniques, the normal endomyocardial biopsy, and the clinical course and were later confirmed in situ.

Pulmonary function in coal workers with Caplan's syndrome and non-rheumatoid complicated pneumosoniosis.

This retrospective study compares the pulmonary function of 24 coal workers with Caplan's syndrome with that of 36 subjects with non-rheumatoid progressive massive fibrosis (PMF). Allowing for differences in radiographical category, age, years worked underground, and smoking, obstruction to air flow as reflected in the one-second forced expiratory volume, the vital capacity, and the ratio of residual volume to total lung capacity, was significantly less in subjects with Caplan's syndrome. No significant differences in transfer factor were found. These findings may be explained by the different pathological features of the two entities. Selection bias does not appear to be responsible for the differences observed between the groups, but studies designed to eliminate this would be desirable.