Diffuse Parenchymal Lung Disease

Diffuse Parenchymal Lung Disease
A heterogeneous group of conditions associated with diffuse thickening of the alveolar walls with inflammatory cells and exudates.
e.g. the acute respiratory distress syndrome-ARDS, granulomas (e.g. sarcoidosis), alveolar haemorrhage (e.g. Goodpasture's syndrome)

General features of DPLD
Gradually progressive shortness of breath on exertion may be the only symptom.
Contact with birds at home or in the working environment is the cause of the most common form of hypersensitivity pneumonitis (HP).
Pulmonary disease may also present in a more insidious manner with cough, exertional breathlessness and radiographic infiltrates; chest auscultation is often surprisingly unremarkable.
The chest X-ray typically shows a fine reticular, reticulonodular or even nodular pattern of infiltration at the bases and periphery with cystic areas and honeycombing in advanced disease.
 Fibrosis occurs in some patients and may cause a silent loss of lung function.
Complications such as bronchiectasis, aspergilloma, pneumothorax, pulmonary hypertension and cor pulmonale but are fortunately rare.
Sarcoidosis
Multisystem granulomatous disease.
Commonly affecting young adults and usually presenting with bilateral hilar lymphadenopathy, pulmonary infiltration and skin or eye lesions.
Unknown aetiology that is often detected by routine chest X-ray.
common in the USA but is uncommon in Japan.
cases of sarcoidosis are seen within families, possibly suggesting an environmental factor.

Immunopathology
Typical sarcoid granulomas consist of focal accumulations of epithelioid cells, macrophages and lymphocytes, mainly T cells.
 Transbronchial biopsies show infiltration of the alveolar walls and interstitial spaces with leucocytes, mainly T cells, prior to granuloma formation.
Histology: non-caeseating epitheloid granuloma.
There is disturbance of calcium metabolism causing hypercalciuria, hypercalcemia and rarely nephrocalcinosis.

PRESENTATION OF SARCOIDOSIS
Asymptomatic-abnormal routine chest X-ray (c. 30%) or abnormal liver function tests
Respiratory and constitutional symptoms (20-30%)
Erythema nodosum and arthralgia (20-30%)
Ocular symptoms (5-10%)
Skin sarcoid (including lupus pernio) (5%)
Superficial lymphadenopathy (5%)
Other (1%), e.g. hypercalcaemia, diabetes insipidus, cranial nerve palsies, cardiac arrhythmias, nephrocalcinosis




Investigations

Imaging. Chest X-ray: BHL, symmetrical, paratracheal nodes enlarged; paranchymal infiltrates, pulmonary fibrosis.
CT is useful for assessment of diffuse lung involvement.
Full blood count. There is mild normochromic, normocytic anaemia with raised ESR.
Serum biochemistry. Serum calcium is often raised and there is hypergammaglobulinaemia.
Transbronchial biopsy is the most useful investigation. Positive results are seen in 90% of cases of pulmonary sarcoidosis with or without X-ray evidence of lung involvement. Pulmonary non-caseating granulomas are found in approximately one-half of patients with clinically extrapulmonary sarcoidosis in whom the chest X-ray is normal.

Serum level of angiotensin-converting enzyme (ACE) is two standard deviations above the normal mean value in over 75% of patients with untreated sarcoidosis. Raised (but lower) levels are also seen in patients with lymphoma, pulmonary tuberculosis, asbestosis and silicosis, limiting the diagnostic value of the test. However, the test is useful in assessing the activity of the disease and therefore as a guide to treatment with corticosteroids. Reduction of serum ACE during treatment with corticosteroids does not, however, reflect resolution of the disease.

Lung function tests show a restrictive lung defect in patients with pulmonary infiltration. There is a decrease in TLC, a decrease in both FEV1 and FVC, and a decrease in gas transfer.
The tuberculin skin test is negative in 80% of patients with sarcoidosis; this is of interest but has no diagnostic value.

Management
The majority of patients enjoy spontaneous remission
'Oral glucocorticoids administered for 6-24 months improve chest X-ray appearances and symptoms but there is little evidence of an improvement in lung function and there are no data from follow-up beyond 2 years.‘
Patients who present with acute illness and erythema nodosum should receive NSAIDs and on occasion a short course of corticosteroids.
Topical steroids may be useful in uveitis but inhaled corticosteroids have no proven benefit in lung disease.
In patients with severe disease both methotrexate and azathioprine have been used successfully
Lung transplantation



Lung disease due to organic dust

Lung disease due to inorganic dust



Asbestosis: the range of possible effects on the respiratory tract.