Caplan syndrome presents with cough and shortness of breath in conjunction with features of rheumatoid arthritis, such as painful joints and morning stiffness. Examination should reveal tender, swollen metacarpophalangeal joints and rheumatoid nodules; auscultation of the chest may reveal diffuse râles that do not disappear on coughing or taking a deep breath. Caplan syndrome is a nodular condition of the lung occurring in dust-exposed persons with either a history of rheumatoid arthritis or who subsequently develop RA within the following 5–10 years. The nodules in the lung typically occur bilaterally and peripherally, on a background of simple coal workers' pneumoconiosis. There are usually multiple nodules, varying in size from 0.5 to 5.0 cm. The nodules typically appear rapidly, often in only a few weeks. Nodules may grow, remain unchanged in size, resolve, or disappear and then reappear. They can cavitate, calcify, or develop air-fluid levels. Grossly, they can resemble a giant silicotic nodule. Histologically, they usually have a necrotic center surrounded by a zone of plasma cells and lymphocytes, and often with a peripheral inflammatory zone made of macrophages and neutrophils.
Causes
Caplan syndrome occurs only in patients with both RA and pneumoconiosis related to mining dust. The condition occurs in miners, asbestosis, silicosis and other pneumoconioses. There is probably also a genetic predisposition, and smoking is thought to be an aggravating factor.
Pathophysiology
The presence of rheumatoid arthritis alters how a person's immune system responds to foreign materials, such as dust from a coal mine. When a person with rheumatoid arthritis is exposed to such offensive materials, they are at an increased risk of developing pneumoconiosis.
Diagnosis
Chest radiology shows multiple, round, well defined nodules, usually 0.5-2.0 cm in diameter, which may cavitate and resemble tuberculosis.
Lung function tests may reveal a mixed restrictive and obstructive ventilatory defect with a loss of lung volume. There may also be irreversible airflow limitation and a reduced DLCO.
The nodules may pre-date the appearance of rheumatoid arthritis by several years. Otherwise prognosis is as for RA; lung disease may remit spontaneously, but pulmonary fibrosis may also progress.
Epidemiology
is currently 1 in 100,000 people but is likely to fall as the coal mining industry declines. It has also been shown to occur in cases of complicated silicosis.
History
The syndrome is named after Dr. Anthony Caplan, a physician on the Cardiff Pneumoconiosis Panel, who identified the constellation of findings as a distinct entity in a 1953 publication. He followed this with further articles exploring the disease. Caplan syndrome was originally described in coal miners with progressive massive fibrosis.
