INTERSTITIAL PULMONARY DISEASES (ILD)
DIFFUSE PARENCHYMAL LUNG DISEASE (DPLD)الدكتور خلدون ذنون- كلية طب نينوى -المرحلة الرابعة
Objectives
The following should be known:1. Definition and causes ILD and how to differentiate it from obstructive lung disease.
2. Importance of imaging and lung function tests in the diagnosis of
DPLD.
3. Features of idiopathic lung fibrosis.
4. Mainstay of therapy: steroid, chemotherapy, lung transplant.
5. Prognosis of lung fibrosis: gloomy.
Introduction
Heterogeneous group of conditions affecting the pulmonary interstitium and alveolar wall.Known causes e.g (asbestos, sarcoidosis), and idiopathic.
Acute e.g drugs, adult respiratory distress syndrome.
Chronic : slowly progressive loss of alveolar-capillary gas
exchange units over month or years.
High resolution CT scan is important first step investigation.
Causes
A. idiopathic interstitial pneumonia
1. Idiopathic pulmonary fibrosis
2. Idiopathic pneumonias of six types.
B. Known causes
Sarcoidosis.
Exposure to organic dust (exposure to organic dust) e.g
farmers lung, bird fancier's lung.
Exposure to inorganic dust e.g asbestosis,silicosis.
Systemic inflammatory disease e.g ARDS, fibrosing alveolitis in
connective tissue disorder e.g SLE,RA.
Pulmonary eosinophilia.
Irradiation &drugs.
Alveolar proteinosis.
CRYPTOGENIC FIBROSING ALVEOLITIS
(Idiopathic pulmonary fibrosis)Cause: unknown (autoimmune, viruses, drugs, GERD, genetic.?)
It is not associated with systemic disease.
Strong association with smoking.
Histopathology: repeated episodes of focal damage to alveolar epithelium with mononuclear cell infiltrate and later fibrosis.
Clinical features
Disease affects mainly those above 50 year age.
Insidious and Progressive exertional dyspnea.
Progressive decline in lung functions and some show acute deterioration and worsening of dyspnea.
Persistent dry cough.
Digital clubbing.
Poor chest expansion.
Bilateral end-inspiratory crackles over lower zones.
In advanced condition: central cyanosis, right ventricular failure.
Investigations
Chest X-rayVirtually all patients have abnormal CXR at presentation.
Small lungs, high hemidiaphragm, bilateral lower zone
&peripheral coarse reticulonodular shadowing.
In advanced disease honeycombing will appear as small cysts.
High resolution CT scan HRCT
Show peripheral and basal reticular pattern with honeycombing.
Lung function
Restrictive defect, decreased vital capacity, FEV1, gas transfer, and lung volume.
Decreased PaO2 initially on exercise, later hypoxia,
hypocapnea are present at rest.
Lung biopsy: done in doubtful cases, usually not required as clinical features and HRCT are sufficient for diagnosis.
Increased gamma globulins, rheumatoid factor & ANF 30-50% +ve.
LDH, CRP, ESR are high and reflect active pneumonitis.
Management
No current curative therapy.
If the vital capacity is between 50% and 80% predicted, patients may be offered either pirfenidone (an antifibrotic agent) or nintedanib (a tyrosine kinase inhibitor).
Both of these agents have been shown to reduce the rate of decline in lung function.
Pirfenidone causes photosensitivity and patient needs sunscreen.
Nintedanib may be accompanied by diarrhoea.
Neither drug improves cough or breathlessness and treatment should be discontinued if lung function declines by more than10% over the first year of treatment.
Advise to stop smoking.
Influenza and pneumococcal vaccination are requested.
Encourage exercise and pulmonary rehabilitation using ambulatory
oxygen if appropriate.
Domiciliary oxygen for severe cases.
Lung transplant: young patient with advanced disease.
For acute exacerbations treatment is largely supportive. Broad-spectrum antibiotics maybe combined with glucocorticoids and sometimes additional immunosuppression.
Prognosis
Median survival 3 years.
Severe cases die within few months.
Some have minimal symptoms & survive for many years.
In majority the disease is progressive.
Oxygen desaturation during exercise indicates poor prognosis.
High number of fibroblastic foci on biopsy suggests more rapid deterioration.
Lung fibrosis is a risk factor for lung cancer.