11/14/24, 10\:59 AM Interstitial Lung Disease

Interstitial Lung Disease

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Key points ⚡
Succinct notes to superpower your revision
Interstitial lung disease (ILD)\: umbrella term for conditions a
Mortality\: particularly high in idiopathic pulmonary
Pathophysiology\: in
compromising gas exchange.
Classi
Primary\: idiopathic pulmonary
Secondary\: connective tissue disease (sarcoidosis, rheumatoid arthritis, SLE), infective (Mycoplasma pneumonia,
Pneumocystis pneumonia), environmental (asbestosis, silicosis), drugs (methotrexate, amiodarone, bleomycin).
Causes of upper and lower zone
Upper zone - (CHARTS), coal-worker pneumoconiosis, histiocytosis-x, ankylosing spondylitis, radiation, tuberculosis,
sarcoidosis and silicosis
Lower zone - (RASIO), rheumatoid arthritis, asbestosis, SLE, scleroderma and Sjogren's syndrome, idiopathic pulmonary

Risk factors\: male sex, cigarette smoking, regular dust exposure.
Symptoms\: progressive exertional dyspnoea, dry cough, symptoms of connective tissue disease, general malaise, and
fatigue.
History\: ask about drug, smoking, occupational, and social history (mould, pets, hobbies).
Examination
(Raynaud’s phenomenon, erythema nodosum), arthritis.
Di
Investigations\:
Bedside\: pulse oximetry, urine dipstick, lung function tests (restrictive pattern).
Laboratory\: FBC, CRP, ESR, U&Es, autoimmune antibodies.
Imaging\: chest X-ray (reticular opacities), high-resolution CT (honeycombing, traction bronchiectasis, reticular opacities).
Invasive\: bronchoalveolar lavage, trans-bronchial/surgical lung biopsy.
Management\:
Conservative\: avoid causes, smoking cessation, pulmonary rehabilitation, vaccines.
Medical\: varies by type (e.g., anti
Long-term oxygen therapy (LTOT)\: indicated if resting PaO2 ≤ 7.3kPa or PaO2 ≤ 8.0kPa with speci
Surgical\: lung transplantation for severe cases.
Complications\:
Disease-related\: respiratory failure, pulmonary hypertension, anxiety, depression.
Treatment-related\: long-term steroid use (osteoporosis, hypertension, Cushing’s syndrome), anti
anorexia).
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Introduction

Interstitial lung disease (ILD) is an umbrella term for a broad spectrum of conditions a
the space between an alveolus and its surrounding capillaries.
1
In the UK, the prevalence of ILD is 50 per 100,000. The commonest type of ILD is idiopathic pulmonary
an incidence of 6,000 new cases per year.
2
Mortality varies across the di
idiopathic pulmonary
3

Aetiology

Pathophysiology

In ILD, there is in
5
Some ILDs (such as sarcoidosis) are predominantly in
and adaptive immune cells and may resolve.
6
Other ILDs (such as idiopathic pulmonary
Fibrosis is triggered by repeated injury to the lung tissue (e.g. from inhaled toxins).
Usually,
mutations lead to excess secretion of extracellular matrix, which accumulates in the lung interstitium, leading to
7
The lung interstitium becomes thicker, increasing the di
the blood in the surrounding capillaries. Hence, gas exchange in the lungs is compromised.
Figure 1. Location of the interstitial space in the lungs.
8
Classi4
Primary (unknown cause)
Idiopathic pulmonary
Acute interstitial pneumonia (can be acute or subacute)
Desquamative interstitial pneumonia (associated with smoking)
Secondary (known cause)
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Connective tissue and autoimmune disease\:
Sarcoidosis
Rheumatoid arthritis
Systemic lupus erythematosus (SLE)
Infective\:
Mycoplasma pneumonia
Pneumocystis pneumonia
Environmental\:
Asbestosis
Silicosis
Drugs\:
Methotrexate
Amiodarone
Bleomycin

Risk Factors

Risk factors for ILD include\:
Male sex
Cigarette smoking
Regular dust exposure (could be occupational)

Clinical features

History

Typical symptoms of ILD include\:
Progressive exertional dyspnoea (usually presents slowly, over many weeks and months)
Dry cough
Connective tissue disease symptoms, such as arthralgia, di
General malaise and fatigue (due to underlying connective tissue disease or vasculitis)
9
Other important areas to cover in the history include\:
Drug history\: ask about any exposure to medications which cause ILD (see "Classi
Smoking history\: quantify in pack-years (1 pack-year = smoking 20 cigarettes a day for a year). Also ask about e-
cigarettes and illicit inhaled substances, such as “crack” cocaine.
10,11
Occupation\: may be exposed to inhaled toxins. Susceptible occupations include farmers (hay dust and A s p e r g i l l u s
mould), bakers (
12
Social history\: ask about the presence of mould and pets at home, and if the patient has any hobbies which increase
exposure to inhaled toxins (such as bird-keeping, which exposes the patient to avian proteins).

Clinical examination

A full respiratory examination should be performed in suspected cases of ILD. Also perform a brief examination of the
patient’s joints, to assess for the presence of connective tissue disease.
Typical clinical
Bilateral
inspiration, which were held closed during the previous expiration.
13
Dullness to percussion\: due to pleural e
14
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Finger clubbing (
extracellular matrix in the nails.
15
Skin signs\: includes Raynaud’s phenomenon in systemic sclerosis (
Arthritis\: due to connective tissue disease.
Figure 2. Finger clubbing.
16

Di

Exertional dyspnoea and cough have important di
the features which di
Table 1. Di
Di
Cough is more productive of sputum
COPD
Lung function tests\: obstructive pattern
(FEV1/FVC \< 70%)
Examination and chest X-Ray\: chest hyperin
Diurnal variation in symptoms and peak
Asthma
History of atopy
Lung function tests\: bronchodilator reversibility
Orthopnoea (dyspnoea while lying down)
Paroxysmal nocturnal dyspnoea (sudden
dyspnoea which wakes the patient up from sleep)
Congestive cardiac failure
Blood tests\: elevated BNP
Echocardiogram\: reduced ejection fraction
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Lung cancer
Bronchiectasis
Signi
Haemoptysis
Imaging\: visible tumour
Cough is more productive of sputum
More frequent lower respiratory tract infections,
often starting in childhood
Lung function tests\: obstructive pattern
(FEV1/FVC \< 70%)

Investigations

Bedside investigations

Pulse oximetry\: aim for 94-98% initially, but the target saturations may be reduced in progressive disease (this is a
decision made by a senior clinician).
Urine dipstick\: haematuria and proteinuria may suggest underlying vasculitis.
19
Lung function tests\: typically show a restrictive pattern (reduced FVC and reduced FEV1), but may also be normal.

Laboratory investigations

FBC\: may show anaemia of chronic disease.
CRP and ESR\: may be elevated.
U&Es\: may be deranged if there is an underlying vasculitis.
Autoimmune antibodies\: anti-CCP suggests rheumatoid arthritis, ANA suggests SLE. Autoimmune antibodies may also
be raised in idiopathic pulmonary
20

Imaging

(table 2).
Chest X-ray (
High-resolution CT (HRCT) (
parenchyma, which is the area a
interstitial pneumonia” pattern, which includes\:
Honeycombing (clusters of cystic airspaces)
Traction bronchiectasis (dilated airways, which are pulled apart by areas of surrounding
Reticular opacities (thickening of the lung interstitium)
Table 2. The causes of upper zone and lower zone
Upper zone
Coal-worker pneumoconiosis
Rheumatoid arthritis
Histiocytosis-X
Asbestosis
Ankylosing spondylitis
SLE, scleroderma and Sjogren’s
syndrome
Radiation (e.g. for breast cancer)
Tuberculosis
Idiopathic pulmonary
Sarcoidosis and silicosis
Others (including drugs)
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Figure 5. Chest x-ray showing lower zone
21

Invasive investigations

Bronchoalveolar lavage (BAL) (
injected through the bronchoscope into the airways. The saline is then collected via suction and analysed. This helps to
diagnose the underlying cause of the ILD, and to also exclude infection or malignancy.
23
Trans-bronchial biopsy/surgical lung biopsy\: a small sample of lung is collected and then analysed by a pathologist. This
may be needed if previous tests are inconclusive, or if a tissue sample is needed to make the diagnosis.
Figure 7.Bronchoscopy. Bronchoalveolar lavage is performed during bronchoscopy.
24

Management

Conservative management

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Avoid any underlying causes (e.g. drug or inhaled toxin)
Smoking cessation
Pulmonary rehabilitation
Annual in

Medical management

Medical management varies for each type of ILD. Some important examples include\:
Idiopathic pulmonary
Sarcoidosis\: corticosteroids (prednisolone).
Connective tissue disease\: corticosteroids and steroid-sparing agents (azathioprine or mycophenolate).
Extrinsic allergic alveolitis\: corticosteroids.
Long-term oxygen therapy (LTOT)
Some patients with ILD may bene
Resting PaO2 ≤ 7.3kPa
Resting PaO2 ≤ 8.0kPa with peripheral oedema/polycythaemia (haematocrit ≥ 55%)/pulmonary hypertension
LTOT is contraindicated in current smokers due to the risk of burns.

Surgical management

Lung transplantation\: for patients with severely impacted quality-of-life, despite optimum medical management.
25

Complications

Disease-related complications

Respiratory failure\: due to failure of gas exchange in the lungs.
Pulmonary hypertension\: due to chronic hypoxic pulmonary vasoconstriction (constriction of blood vessels supplying

26
Anxiety and depression\: due to impaired quality-of-life.

Treatment-related complications

Due to long-term steroid use\: osteoporosis, hypertension, Cushing’s syndrome.
Due to anti

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Reviewer

Dr Neeraj Shah
Respiratory Medicine Registrar

Related notes

Asthma
Bronchiectasis
Chronic Obstructive Pulmonary Disease (COPD)
Croup
Cystic Fibrosis
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