If left untreated, some patients might develop irreversible pulmonary fibrosis.

• The patients with Caplan syndrome are mostly asymptomatic initially. ^{[1] [2]}
• Caplan nodules appear with or later than the onset of Rheumatoid arthritis.^[3]
• Caplan nodules may lead to cavitation or calcification with pleural effusion or in rare cases pneumothorax.
• Lung nodules in Caplan syndrome are rapidly growing; gain final size within weeks to month and then remain unchanged for years long.
• Most of the lung nodules resolve spontaneously while some leave behind asteroid scarring. In 10% cases, cavitation and calcification happen.
• There are cases of Caplan syndrome with radiologic findings of Caplan nodules but no rheumatoid factor.
• The symptoms of dyspnea and cough typically develop with the progression of the disease.
• If left untreated, patients with Caplan syndrome may progress to develop wheeze in the chest which doesn’t change with cough suggestive of irreversible pulmonary fibrosis.

Possible complications include^{[3] [4]}:

• Increased risk for tuberculosis and aspergillosis
• Hemoptysis
• Pleural effusion
• Pneumothorax
• Progressive massive fibrosis (scarring)
• Side effects of medications

Caplan syndrome rarely causes serious breathing trouble or disability due to lung problems.^[4]

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.