Chronic Dyspnea

Christopher M. Walker, MD

DIFFERENTIAL DIAGNOSIS

Common

Pleural Effusion
Emphysema
Sarcoidosis
Bronchogenic Carcinoma

Less Common

Usual Interstitial Pneumonia
Nonspecific Interstitial Pneumonia
Respiratory Bronchiolitis-associated Interstitial Lung Disease
Radiation Pneumonitis
Mycobacterial Avium Complex
Lymphangitic Carcinomatosis
Pneumoconioses
Left to Right Shunt

Rare but Important

Bronchioloalveolar Cell Carcinoma
Constrictive Bronchiolitis
Lymphocytic Interstitial Pneumonia
Pulmonary Alveolar Proteinosis
Chronic Eosinophilic Pneumonia
Organizing Pneumonia
Lipoid Pneumonia
Langerhans Cell Histiocytosis
Lymphangiomyomatosis
Hypersensitivity Pneumonitis
Desquamative Interstitial Pneumonia

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Review focuses on adult intrathoracic causes of dyspnea lasting weeks to years

Helpful Clues for Common Diagnoses

Pleural Effusion
- Exudative effusions
  - Pleural thickening/enhancement in 60%
  - Infections, malignancy, connective tissue diseases, and asbestos exposure
Emphysema
- Flat diaphragm and increased retrosternal clear space
Sarcoidosis
- Symmetric right paratracheal, right hilar, and left hilar lymphadenopathy is called 1-2-3 sign or Garland triad
- Perilymphatic lung nodules (nodules along fissures, subpleural lung, and bronchovascular bundles)
Bronchogenic Carcinoma
- Nodule or mass in current/former smoker

Helpful Clues for Less Common Diagnoses

Usual Interstitial Pneumonia
- Basal and subpleural fibrosis with honeycombing
- ± mediastinal lymphadenopathy
- Most common cause is idiopathic pulmonary fibrosis
Nonspecific Interstitial Pneumonia
- Associated with collagen vascular diseases
- Lower lobe and peripheral ground-glass opacity
- ± subpleural sparing
- Honeycombing rare
Respiratory Bronchiolitis-associated Interstitial Lung Disease
- Symptomatic smoker
- Upper lung centrilobular nodules of ground-glass opacity
Radiation Pneumonitis
- 1-4 months following radiation therapy
- Ground-glass opacity with sharp borders
  - Disobeys anatomic boundaries
Mycobacterium Avium Complex
- Older women
- Middle lobe and lingular bronchiectasis
- Tree in bud centrilobular opacities
Lymphangitic Carcinomatosis
- Smooth or nodular thickening of interlobular septa
- ± hilar or mediastinal lymphadenopathy
- ± pleural effusion
Pneumoconioses
- Asbestosis
  - Posterobasal and subpleural lung
  - Bilateral pleural plaques
  - Honeycombing and thickened septa late
- Silicosis and coal worker’s pneumoconiosis
  - Posterior upper lung predominant
  - Centrilobular and subpleural nodules
  - Nodules may coalesce to form progressive massive fibrosis
Left to Right Shunt
- ASD and partial anomalous pulmonary venous return are most common etiologies in adults

Helpful Clues for Rare Diagnoses

Bronchioloalveolar Cell Carcinoma
- Most common presentation
  - Solitary pulmonary nodule
- Chronic ground-glass opacity
  - ± “pseudocavitation” with cystic spaces
Constrictive Bronchiolitis
- Synonyms
  - Bronchiolitis obliterans or obliterative bronchiolitis
- Causes include
  - Infection, toxic fume inhalation, collagen vascular diseases, and chronic rejection
- Bronchiectasis, mosaic perfusion, and expiratory air-trapping
Lymphocytic Interstitial Pneumonia
- Strong association with Sjögren syndrome
- AIDS defining in children
- Ground-glass opacity and nodules ± isolated or diffuse lung cysts
Pulmonary Alveolar Proteinosis
- Crazy-paving pattern
  - Geographic bilateral ground-glass opacities with interlobular septal thickening
- Idiopathic or seen with silicosis, malignancy, and chemotherapeutic medications
- Exclude acute causes of crazy-paving, such as ARDS by history
Chronic Eosinophilic Pneumonia
- Peripheral upper lung consolidation
- Blood eosinophilia
Organizing Pneumonia
- Idiopathic, collagen vascular diseases, and infections
- Lower lobe and peripheral ground-glass opacity, small nodules, or focal consolidation
- “Atoll” or “reverse halo” sign
Lipoid Pneumonia
- Aspiration of oils used for laxatives
- Lower lobe consolidation or mass
  - Central low-attenuation areas (-80 to -30 HU)
Langerhans Cell Histiocytosis
- Centrilobular nodules ± central cavitation
- Costophrenic angles spared
- Round or bizarrely shaped cysts in upper lungs
Lymphangiomyomatosis
- Women of childbearing age
- Large lung volumes with chylous effusions and pneumothoraces
- Numerous diffuse round lung cysts
Hypersensitivity Pneumonitis
- Centrilobular nodules of ground-glass opacity
- “Head-cheese” sign: Ground-glass opacity, decreased lung attenuation, and normal lung
Desquamative Interstitial Pneumonia
- Diffuse/patchy ground-glass opacity
- ± cystic lesions or centrilobular emphysema
- ± lower lobe predominance

Image Gallery

Coronal CECT shows a chronic pleural effusion

in this patient with lupus. Note separate loculated fluid collection

with an enhancing pleural lining indicating its exudative nature.

Frontal radiograph shows a left-sided pleural fluid collection

that was unchanged over months. Pleural effusion/thickening is the most common thoracic manifestation seen in patients with lupus.

(Left) Axial CECT shows severe centrilobular emphysema with near complete destruction of the secondary pulmonary lobule. Note preservation of centrilobular core structures