Rheumatoid Necrobiotic Nodules

Helen T. Winer-Muram, MD

Key Facts

Terminology

Subacute or chronic inflammatory polyarthropathy of unknown cause

Imaging Findings

Rheumatoid nodules (seen in < 5%)
- Solitary or multiple, 0.5-7 cm, few in number
- Peripheral (subpleural)
- Cavitation (50%)
- May contain necrotic lung ball or rarely mycetoma
- May result in pneumothorax (may be refractory to therapy)
- Wax & wane
Caplan syndrome: Rare
- Hypersensitivity reaction to dust
- Associated with coal miner’s pneumoconiosis
- Large rounded nodules (0.5-5 cm), may cavitate
Rheumatoid arthritis nodules may have uptake on PET

Top Differential Diagnoses

Tuberculosis
Histoplasmosis
Metastases
Amyloid Nodules

Pathology

Nodules identical to subcutaneous nodules

Clinical Issues

Rheumatoid nodules, more common in males, especially smokers

Diagnostic Checklist

Need to rule out infectious etiology for nodules prior to initiation of immunosuppression

Axial NECT shows multiple solid

and cavitary

pulmonary nodules from rheumatoid arthritis.

Axial NECT in the same patient shows large peripheral cavitary nodules with variable wall thickness

from rheumatoid necrobiotic nodules.

TERMINOLOGY

Abbreviations and Synonyms

Rheumatoid arthritis (RA)
Caplan syndrome, rheumatoid pneumoconiosis

Definitions

Subacute or chronic inflammatory polyarthropathy of unknown cause

IMAGING FINDINGS

General Features

Best diagnostic clue: Chronic pleural effusion and lung nodules in patient with rheumatoid arthritis
Patient position/location: Peripheral subpleural
Size: Variable, usually < 1 cm diameter
Morphology: Solid or cavitary nodules

CT Findings

Rheumatoid nodules (seen in < 5%)
- Morphology
  - Solitary or multiple, 0.5-7 cm, few in number
  - Usually well circumscribed
  - Resemble neoplasm, discrete, rounded, or lobulated
  - May rarely calcify
  - Identical to subcutaneous nodules (usually seen around elbows)
- Cavitation (50%)
  - Thick or thin smooth wall
  - May contain necrotic lung ball or rarely mycetoma
  - May result in pneumothorax (may be refractory to therapy)
- Distribution
  - Peripheral (subpleural)
- Evolution
  - Wax & wane
Caplan syndrome: Rare
- Hypersensitivity reaction to dust
- Associated with coal miner’s pneumoconiosis
- Redefined to include silica, asbestos, dolomite, carbon
- Large rounded nodules (0.5-5 cm), may cavitate
- Indistinguishable from silicate pneumoconiotic nodules or tuberculous nodules
- Nodules have peripheral distribution
- Serologic but not clinical rheumatoid arthritis
Other associated pleuropulmonary abnormalities
- Pleural disease
  - Most common abnormality in RA
  - Pleural effusions or thickening from fibrothorax
  - Effusions small to large
  - Effusions usually unilateral, transient, persistent, or relapsing
  - May be associated with rheumatoid nodules and subcutaneous nodules
  - Pleural abnormalities and pulmonary nodules, if present, help distinguish RA-related interstitial lung disease
Interstitial pneumonitis & fibrosis
- Most common pulmonary abnormality (30-40%)
- Nonspecific interstitial pneumonia or usual interstitial pneumonia
Cryptogenic organizing pneumonia pattern
- Ground-glass opacities, nodules, bronchovascular distribution
Airways disease
- Bronchiectasis, follicular bronchiolitis, constrictive bronchiolitis

Radiographic Findings

Nodules may appear in crops, persist or resolve spontaneously, wax & wane
Serial radiography for surveillance
- Development of new nodules
- Stability or resolution of nodules
- Progression: Increasing size and number of nodules, development of cavitation
- Development of pleuropulmonary complications