• Cryptogenic Fibrosing Alveolitis (CFA) / Idiopathic Pulmonary Fibrosis (IPF)

    by  • 01/06/2013 • Respiratory

    Cryptogenic fibrosing alveolitis (CFA) / Idiopathic pulmonary fibrosis (IPF)

    Definition

    1. Most common RLD
    2. Diffuse fibrosis throughout the interstitium of the lung fields
    3. If clear RLD = but no obvious cause: CFA/IPF

     

    Who

    1. Late-middle age (occurs in 6th decade >50).

     

    Presentation

    1. Progressive dyspnoea
    2. Cyanosis
      1. o Both eventually lead to respiratory failure, pulmonary hypertension and cor pulmonale
    3. Gross finger clubbing
    4. Fine bilateral end-inspiratory crackles
    5. Acute interstitial pneumonitis/acute CFA = Hamman-Rich syndrome (a form of ARDS)
    6. Chest xray shows ground-glass appearance, progressing to obvious small nodular shadows with streaky fibrosis and honeycomb lung.

     

    Diagnostic/Investigation

    1. CXR
      1. o Irregular bilateral reticulonodular shadowing in lower zones
    2. High resolution CT scan
      1. o Characteristic changes of peripheral reticular and ground-glass opacification.
      2. o Seen best in the basal regions but extending over the lungs
    3. Respiratory function tests
      1. o Restrictive ventilatory defect
      2. o Low TLV, FEV1:FVC is normal to high = RLD!!
      3. o Carbon monoxide gas transfer is reduced
    4. Blood gases
      1. o Arterial hypoxaemia caused by alveolar-capillary block and ventilation-perfusion mismatch
      2. o Normal or low PaCO2 due to hyperventilation
    5. Blood tests
      1. o Antinuclear antibodies and rheumatoid factors +ve! (in 1/3rd of patients).
      2. o ESR and immunoglobulins are mildly elevated.
    6. Bronchoalveolar lavage
      1. o Increased numbers of cells, particularly neutrophils and macrophages.
    7. Histological confirmation
      1. o Transbronchial lung biopsy is rarely diagnostic but can exclude other conditions such as sarcoidosis or lymphangitis carcinomatosa.

     

    Aetiology – cause, risk factors

    Occupational exposure to metal or wood dust

    Many patients show features of autoimmunity

    Reported in association with:

    1. Coeliac disease
    2. Ulcerative colitis
    3. Renal tubular acidosis
    4. Primary biliary cirrhosis

     

    Pathophysiology

    Macrophages and alveolar epithelial cells are activated.

    Produce growth factors:

    1. Fibronectin
    2. Platelet-derived growth factor (PDGF)

     

    1. Transforming growth factor-beta (TGF-beta)
    2. Insulin-like growth factor-1 (IGF-1)

     

    Stimulate deposition of type 1 and type 3 collagens.

    Histologically there are 2 main features:

    1. 1. Cellular infiltration with T lymphocytes and plasma cells and thickening and fibrosis of alveolar walls
    2. 2. Alveolitis – increased cells within the alveolar space (mainly macrophages and type II pneumocytes shed from the alveolar walls)

     

    Treatment/management

    Treatment with prednisolone

    Add Azathioprine, methotrexate or cyclophosphamide if no response – same approach as silicosis!

    Prognosis

    Median survival time is approximately 5 years = poor prognosis. 

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