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.
Some will respond to corticosteroid & immunosuppressive agent
the indications are :
1. Patient with prominent symptoms.
2. Rapid disease progression.
3. Ground glass appearance on CT.
4. Sustained fall of >15% in FVC or gas transfer over 3-6 month.
Prednisone 0.5 mg/kg with azathioprine 2mg/kg. if there is a response maintain steroid dose at 10-12.5 mg/day.
Response is poor, in addition drug side effects.
Oxygen to palliate dyspnea.
Opiates may be required in severe dyspnea.
Lung transplant: young patient with advanced disease.
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.