Diffuse Parenchymal Lung Disease Quiz

Diffuse Parenchymal Lung Disease

• Heterogeneous group of conditions affecting the pulmonary parenchyma (interstitium) and/or alveolar lumen
• Shares clinical, physiological, and radiographic similarities

Clinical Presentation

• Cough: usually dry, persistent, and distressing
• Breathlessness: usually slowly progressive, insidious onset, acute in some cases
• Examination findings:
  • Crackles: typically bilateral and basal
  • Clubbing: common in idiopathic pulmonary fibrosis, also seen in other types (e.g., asbestosis)
  • Central cyanosis and signs of right heart failure in advanced disease (corpulmonale)

Radiology

• Chest X-ray: typically small lung volumes with reticulonodular shadowing, but may be normal in early or limited disease
• High-resolution computed tomography: combinations of ground glass changes, reticulonodular shadowing, honeycomb cysts, and traction bronchiectasis, depending on stage of disease

PFT

• Typically restrictive ventilatory defect with reduced lung volumes and impaired gas transfer
• Exercise tests assess exercise tolerance and exercise-related fall in SaO2

Acute Interstitial Pneumonia

• Organizing pneumonia
• Bronchopneumonia
• Pulmonary oedema

Conditions that Mimic Diffuse Parenchymal Lung Disease

• Infection:
  • Viral pneumonia
  • Tuberculosis
  • Pneumocystis jirovecii
  • Parasite (e.g., lariasis)
  • Fungal infection
• Malignancy:
  • Leukemia and lymphoma
  • Multiple metastases
  • Lymphangitic carcinomatosis
  • Bronchoalveolar carcinoma
• Pulmonary oedema
• Aspiration pneumonia

Laboratory Investigations

• Full blood count: lymphopenia in sarcoidosis, eosinophilia in pulmonary eosinophilias and drug reactions, neutrophilia in hypersensitivity pneumonitis
• Erythrocyte sedimentation rate and C-reactive protein: non-specifically raised
• Ca2+: may be elevated in sarcoidosis
• Serum angiotensin-converting enzyme: non-specific indicator of disease activity in sarcoidosis
• Lactate dehydrogenase: may be elevated in active alveolitis
• Autoimmune screen: anti-cyclic citrullinated peptide (anti-CCP) and other autoantibodies may suggest connective tissue disease

Radiology and PFT

• Chest X-ray and high-resolution computed tomography
• PFT: typically restrictive ventilatory defect with reduced lung volumes and impaired gas transfer

Bronchoscopy and Biopsy

• Bronchoscope: differential cell counts may point to sarcoidosis, drug-induced pneumonitis, pulmonary eosinophilias, hypersensitivity pneumonitis, or cryptogenic organizing pneumonia
• Transbronchial biopsy: useful in sarcoidosis and differential of malignancy or infection
• Video-assisted thoracoscopic lung biopsy (VATS): allows pathological classification, presence of asbestos bodies may suggest asbestosis, silica in occupational fibrosing lung disease

Idiopathic Pulmonary Fibrosis

• Defined as a progressive fibrosing interstitial pneumonia of unknown cause, occurring in adults and associated with the histological or radiological pattern of UIP
• Important differentials include fibrosing diseases caused by occupational exposure, medication, or connective tissue diseases
• Histological features suggest repeated episodes of focal damage to the alveolar epithelium
• Familial cases are rare, but genetic factors that control the inflammatory and fibrotic response are likely to be important
• Strong association with cigarette smoking

Clinical Features of IPF

• Presents in older adults, uncommon before the age of 50 years
• May present as an incidental finding on CT scan or with progressive breathlessness and a non-productive cough
• Constitutional symptoms are unusual
• Clinical findings include finger clubbing and bi-basal fine late inspiratory crackles

Investigations for IPF

• Full blood count, erythrocyte sedimentation rate, and C-reactive protein
• Chest X-ray and high-resolution computed tomography
• Bronchoscope: lymphocytosis may suggest chronic hypersensitivity pneumonitis
• Surgical lung biopsy: should be sought if necessary

Treatment of IPF

• Pirfenidone (an antifibrotic agent) or nintedanib (a tyrosine kinase inhibitor) may be offered
• Both agents have been shown to reduce the rate of decline in lung function
• Neither drug improves cough or breathlessness, and treatment should be discontinued if lung function declines by more than 10% over the first year of treatment
• Medication to control gastro-oesophageal reflux may improve the cough
• Stop smoking, oxygen therapy, and lung transplantation may be considered

Prognosis of IPF

• Median survival of 3 years is widely quoted
• Rate of disease progression varies considerably

Pneumoconiosis

• Permanent alteration of lung structure due to the inhalation of mineral dust and the tissue reactions of the lung to its presence
• Important pneumoconiosis include coal worker's pneumoconiosis, silicosis, and asbestosis

Coal Worker's Pneumoconiosis (CWP)

• Follows prolonged inhalation of coal dust, resulting in a fibrotic reaction and the appearance of scattered discrete fibrotic lesions
• Classification is based on the size and extent of radiographic nodularity
• Simple coal worker's pneumoconiosis (SCWP) refers to the appearance of small radiographic nodules in an otherwise asymptomatic individual
• Progressive massive fibrosis (PMF) refers to the formation of one or more conglomerate masses more than 1 cm in diameter
• Treatment involves removing or reducing coal dust exposure, and is otherwise supportive treatment
• PMF may progress, even after coal dust exposure ceases, and in extreme cases leads to respiratory failure and right ventricular failure
• CWP is not associated with increased risk of lung cancer
• Caplan syndrome describes the coexistence of rheumatoid arthritis and rounded fibrotic nodules 0.5-5 cm in diameter

Silicosis

• Results from the inhalation of crystalline silica, usually in the form of quartz, by workers cutting, grinding, and polishing stone
• Patients experience dry cough and breathlessness with the sensation of chest restriction
• Classic or sub-acute silicosis is most common and usually manifests after 10-20 years of continuous silica exposure
• Accelerated silicosis is associated with a much shorter duration of dust exposure (typically 5-10 years), may present as early as after 1 year of exposure, and follows a more aggressive course
• Intense exposure to very fine crystalline silica dust can cause a more acute disease: silicoproteinosis
• Chronic silicosis can develop after 10-30 years of continuous exposure to lower concentrations of silica dust
• Treatment, aside from stopping exposure, is mainly supportive
• Increased risk of TB (silicotuberculosis), non-tuberculous mycobacterial infection, lung cancer, and COPD