A 50-year-old man with a 10-year history of rheumatoid arthritis (RA) presents to the clinic with worsening shortness of breath and a persistent dry cough over the past few months. He works as a coal miner and has a history of significant occupational exposure to coal dust. A chest X-ray reveals multiple well-defined nodules in both lung fields, particularly in the upper lobes, along with features of mild interstitial lung disease.
What is the most likely diagnosis?
A. Systemic lupus erythematosus (SLE)
B. Reactive arthritis
C. Psoriatic arthritis
D. Rheumatoid arthritis
E. Gout
Correct Answer: D. Rheumatoid arthritis
Detailed Explanation:
Caplan’s syndrome, also known as rheumatoid pneumoconiosis, is a rare complication of rheumatoid arthritis (RA). It is characterized by the presence of multiple pulmonary nodules in individuals with RA who have been exposed to occupational dust, such as coal, silica, or asbestos. This condition results from an interplay between the autoimmune response in RA and environmental exposure.
Key features of Caplan’s syndrome:
- Pulmonary nodules: Well-defined, rounded lesions visible on imaging, typically in the upper lobes.
- Rheumatoid arthritis: Long-standing history of RA, which can include joint pain, stiffness, and swelling.
- Environmental exposure: A history of working in industries with significant exposure to dust (e.g., mining).
The nodules can sometimes cavitate or lead to secondary infections. Symptoms include:
- Progressive dyspnea (shortness of breath).
- Persistent cough.
- Occasionally, constitutional symptoms like fever and weight loss, although these are less common.
Diagnosis involves:
- Chest X-ray or CT scan: Demonstrating nodules and interstitial changes.
- Pulmonary function tests (PFTs): May show restrictive or mixed patterns in advanced disease.
- Rheumatoid factor (RF) and anti-CCP antibodies: Usually positive, confirming RA.
Treatment focuses on managing the underlying RA and mitigating exposure to harmful dust. Severe cases may require immunosuppressive therapy or oxygen support.
Why Other Options Are Incorrect:
A. Systemic lupus erythematosus (SLE)
SLE can cause pleuritis, pulmonary fibrosis, and alveolar hemorrhage, but it does not cause Caplan’s syndrome or dust-related pulmonary nodules.
B. Reactive arthritis
Reactive arthritis is associated with inflammatory joint symptoms and may involve uveitis, conjunctivitis, or urethritis, but it is not linked to pulmonary complications or nodules.
C. Psoriatic arthritis
Psoriatic arthritis typically affects the joints and skin, presenting with psoriasis. Pulmonary involvement is not characteristic of this condition.
E. Gout
Gout involves monosodium urate crystal deposition in joints, causing painful arthritis. It is unrelated to pulmonary diseases.