Document 6505269

Clinical Review
For the full versions of these articles see bmj.com
1
Department of Respiratory
Medicine, Aberdeen Royal
Infirmary, Foresterhill, Aberdeen
AB25 2ZN
2
Aberdeen University Medical
School, Foresterhill, Aberdeen
AB25 2ZD
3
Department of Cardiothoracic
1294
BMJ | 12 june 2010 | Volume 340
CLINICAL REVIEW
Interstitial lung diseases (ILD)
ILD of known cause – eg,
drug, dusts, connective
tissue diseases
ILD of unknown cause
(“idiopathic interstitial
pneumonias”)
Idiopathic pulmonary fibrosis (IPF)
Granulomatous ILD –
eg, sarcoidosis
Other rare
causes of ILD
Six other “non-IPF” conditions –
eg, non-specific interstitial pneumonia (NSIP)
Fig 3 | Current classification of interstitial lung disease.3 Idiopathic interstitial pneumonias
refers to a group of seven related interstitial lung diseases, the most common of which is
idiopathic pulmonary fibrosis (formerly known as cryptogenic fibrosing alveolitis), which has a
particularly poor prognosis
What questions are important to ask?
Medication history
Box 1 lists medications that may be associated with adverse
effects in the lung. Prescribed and “over the counter” medications, herbal therapies, and illicit drugs have been associated with interstitial lung diseases; www.pneumotox.com
provides information about drug induced lung disease.12 13
Drug induced interstitial lung disease is straightforward
to recognise if it develops within days of prescription, but
presentation may be subacute (over months) or chronic
(years) even with the same drug (for example, nitrofurantoin).14 15 Similarly, various pathological patterns of interstitial lung disease can occur for the same drug (for example,
methotrexate) ranging from a relatively benign interstitial
pneumonitis through to life threatening diffuse alveolar
damage. If recognised early enough, most forms of drug
induced interstitial lung disease are reversible.12 13
History of a connective tissue disease
Any of the connective tissue diseases may be complicated
by interstitial lung disease.10 16 17 Occasionally patients
present with pulmonary symptoms before rheumatological manifestations become obvious. Clinical clues to the
possibility of an underlying connective tissue disease are
shown in figure 6.
Environmental exposures
Hobbies, occupation, travel, and other possible environmental exposures should be taken into account. Taking
a detailed current and previous occupational history
Fig 5 | Hypersensitivity pneumonitis resulting from dust
exposure. A typical computed tomography image is shown
with diffuse centrilobular ground glass nodules.
can be time consuming;18 a practical solution is to ask
patients in advance to prepare a chronological list of
jobs and to bring this list to their initial assessment.
Inorganic dusts linked with interstitial lung disease
include asbestos,19 coal and silica,20 and beryllium.21
New industries have generated new forms of interstitial
lung disease, such as flockworker’s lung in manufacturers of synthetic microfibres (flock) of nylon, 22 and
metalworker’s lung in those exposed to metalworking
fluid aerosol.23 Hypersensitivity pneumonitis can be
caused by antigens in organic dusts, such as Saccha­
ropolyspora rectivirgula in hay, which causes farmer’s
lung, and proteins in bird droppings and on feathers
that cause bird or pigeon fancier’s lung.11 Case reports
have associated feathers in duvets with hypersensitivity
pneumonitis.24 25 and more than 20 case reports have
linked domestic mould exposure with hypersensitivity
pneumonitis.26 27
Questions about recreational activities and travel
may reveal an important exposure—for example, Myco­
bacterium avium complex causes “hot tub lung” and
Trichoderma koningii “woodworker’s lung.”28 A metaanalysis of six case-control studies conducted in the UK,
United States, and Japan reported that smoking (odds
ratio 1.58, 95% confidence interval 1.27 to 1.97), agriculture or farming (1.65, 1.20 to 2.26), livestock (2.17,
1.28 to 3.68), wood dust (1.94, 1.34 to 2.81), metal
Fig 4 | Idiopathic pulmonary fibrosis. (A) Digital clubbing is commonly, but not always, seen. (B) Chest radiograph noting small lungs with bilateral subpleural
shadowing with a lower zone predominance (arrows). (C) Computed tomography noting gross abnormalities of both lungs including intralobular and interlobular
septal thickening with honeycombing
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CLINICAL REVIEW
Box 1 | Examples of drugs that can cause interstitial lung
disease12 13
•Antibiotics—cephalosporin, minocycline, nitrofurantoin,
quinine
•Rheumatology treatments—gold, leflunomide,
methotrexate, NSAIDs, penicillamine, sulphasalazine,
tumour necrosis factor α blockers (infliximab, etanercept)
•Cardiology treatments—amiodarone, angiotensin
converting enzyme inhibitors, aspirin, atenolol, statins
•Oncology treatments—bleomycin, busulfan,
chlorambucil, melphalan, methotrexate, mitomycin C,
tyrosine kinase inhibitors (dasatnib, imatinib)
•Illicit drugs—cocaine, heroin, intravenous talc,
methadone
•Immunomodulators—azathioprine, cyclophosphamide,
epidermal growth factor receptor inhibitors (gefitinib,
erlotinib), interferons, methotrexate, rapamycin
derivatives (sirolimus), tumour necrosis factor α blockers,
rituxumab
•Miscellaneous—high flow oxygen, inhalation or
aspiration of fat-containing substances (drugs containing
mineral oils, certain laxatives, petroleum jelly), paraquat,
radiotherapy
dust (2.44, 1.74 to 3.40), and stone or sand (1.97, 1.09
to 3.55) were associated with an increased risk of idiopathic pulmonary fibrosis.29
Smoking
Cigarette smoking is associated with several interstitial lung
diseases.30 31 A recent population based cohort study of 2563
adults in the United States suggested that smoking may cause
subclinical parenchymal lung disease that is detectable by
spirometry and computed tomography imaging.32 Curiously,
Fever, fatigue
Sarcoidosis
Eye signs – eg, uveitis
Sarcoidosis
Any neurological signs
– eg, facial nerve palsy
Sarcoidosis, vasculitis
Peripheral lymphadenopathy
Sarcoidosis
Facial telangectasiae
Scleroderma
Facial rash
Systemic lupus erythematosus
Crackles on auscultation
Any interstitial lung disease
Digital clubbing
Pulmonary fibrosis
NB many other causes
including lung cancer
Hepatosplenomegaly
Sarcoidosis
Subcutaneous nodules
Rheumatoid
Digital ulceration/
thickened skin/
Raynaud’s
Scleroderma
Muscle tenderness/proximal weakness
Polymyositis
Heliotrope rash
Dermatomyositis
Joint swelling/arthritis
Any connective tissue disease
– eg, rheumatoid
Erythema nodosum/ankle arthralgia
Sarcoidosis
Fig 6 | Possible clinical manifestations of interstitial lung disease
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some forms of interstitial lung disease, such as hypersensitivity pneumonitis and sarcoidosis, are less common in smokers.33 34
Family history
Although familial clustering is well described for sarcoidosis,35 36 familial idiopathic pulmonary fibrosis is rare, accounting for only 0.5-2.2% of all cases.37
Gastro-oesophageal reflux
The nature of an observed link between chronic recurrent
microaspiration of gastric acid and the development of
chronic lung disease is not clear.38 The prevalence of reflux
is increased in patients with idiopathic pulmonary fibrosis
and scleroderma lung, although whether its development
and course can be influenced by anti-reflux treatment is not
known.39 40
What are the key features on examination?
Clinical examination does not always reveal signs of illness.
However, inspiratory crackles may be heard on chest auscultation.2 Crackles are typically best heard over the lower lobes
and axillary regions in patients with idiopathic pulmonary
fibrosis. In those with sarcoidosis crackles may be absent,
despite radiological abnormality. Mid-inspiratory “squeaks”
are suggestive of bronchiolitis. Clubbing of the fingers occurs
in about half of patients with idiopathic pulmonary fibrosis
and may accompany other interstitial lung diseases. If interstitial lung disease is advanced patients may be cyanosed and
show signs of secondary pulmonary arterial hypertension.41
Examples of extrapulmonary signs that may occur are shown
in figure 6.
What first line investigations should be considered before
referral?
Figure 7 outlines the initial assessment of patients with suspected interstitial lung disease. Full history and examination
may identify known causes of such disease and will help
direct subsequent investigations.
Chest radiograph
The chest radiograph can be normal in early interstitial lung
disease.42 By the time the disease is clinically apparent chest
radiographs will usually be abnormal. Abnormalities include
decreased lung volumes, sub­pleural reticular opacities,
peripheral migratory air space shadowing, and mediastinal
or hilar lymph node enlargement. For example, bilateral hilar
lymphadenopathy with upper lobe pulmonary infiltrates in a
young adult suggests s­arcoidosis; basal fibrosis with pleural
thickening and pleural plaques suggests asbestosis. The chest
radiograph may also help to identify lung cancer, infection,
or pneumothorax, which may be associated with interstitial
disease. Chest radiography has limited sensitivity and lacks
specificity for diagnosing subtypes of interstitial lung disease; high resolution computed tomography is more useful
in diagnosis and differentiation.1
Oximetry
An oxygen saturation of less than 94% at rest is abnormal
and should prompt referral for more detailed assessment by
a chest physician.
BMJ | 12 june 2010 | Volume 340
CLINICAL REVIEW
Blood tests
A full blood count, including eosinophils, and a serum
biochemistry profile (including renal and liver function
tests, calcium, glucose, thyroid function, C reactive protein) are potentially useful baseline investigations in combination with clinical and radiological findings.
(such as Saccharopolyspora rectivirgula, Thermactino­
mycetes vulgaris, Aspergillus for mouldy hay).
British Thoracic Society guidelines suggest that measurement of serum angiotensin converting enzyme has a
limited role in the diagnosis of suspected sarcoidosis and
does not contribute to monitoring patients when added to
serial lung function and imaging.1 Furthermore, assays to
detect the enzyme have limited sensitivity and specificity
and values are affected by angiotensin converting enzyme
gene polymorphisms.48 Levels of angiotensin converting enzyme are raised in many other conditions including other granulomatous diseases (leprosy, tuberculosis,
h­istoplasmosis), Gaucher’s disease, and hyperthyroidism.49
Results are invalidated if a patient is taking an angiotensin
converting enzyme inhibitor.
Testing for HIV infection may be helpful, since some
forms of interstitial lung disease are associated with
immunodeficiency, such as lymphocytic interstitial pneumonia.50 Brain natriuretic peptide, secreted in response to
ventricular stretch by cardiomyocytes, is a marker of right
ventricular dysfunction. Although the test is not available
in all centres, some studies in patients with interstitial
lung disease suggest that elevated levels of the peptide
can identify patients with pulmonary hypertension and
poorer prognosis.51‑54 A wide range of serum biomarkers
(lung epithelium specific proteins, cytokines, and other
biological markers of cellular activity) may also theoretically reflect more severe or widespread interstitial lung
disease.55 However, as yet, no perfect biomarker has been
identified, and since the tests are costly and of uncertain
clinical usefulness their role is unclear.56
Urinalysis
Haematuria or proteinuria may strengthen suspicion of an
underling systemic vasculitis.43 A 24 hour urine collection
may identify hypercalcuria in suspected sarcoidosis.44‑46
What is the role of high resolution computed
tomography?
Typical reasons for high resolution computed tomography
in interstitial lung disease are:
•
Electrocardiogram
Since many patients who present with a cough and
breathlessness may also have a history of smoking and
other c­ardiovascular risk factors, a baseline electrocardiogram is necessary. It may show signs of right ventricular
strain, prompting further investigation of suspected secondary pulmonary vascular disease. Rarely, conduction
defects and arrhythmias are found in patients with cardiac
s­arcoidosis.47
What are the second line investigations?
An algorithm for further investigation is presented in figure
7. Some approaches are discussed here.
Other blood tests
An arterial blood gas is needed to confirm respiratory failure in patients with a resting oxygen saturation of less than
94%, in those who are polycythaemic and those with signs
suggestive of cor pulmonale. If a connective tissue disease
is suspected then an immunology screen (antinuclear antibody, extractable nuclear antigens, rheumatoid factor, and
anti-neutrophil cytoplasmic antibody) will be required. If
an environmental factor is suspected, specific serum IgG
antibody screens can be performed for relevant antigens
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CLINICAL REVIEW
ADDITIONAL EDUCATIONAL RESOURCES
Resources for healthcare professionals
British Thoracic Society (www.brit-thoracic.org.uk)—Recent
guidelines on the management of interstitial lung
diseases, with useful patient information sheets and
management algorithms
American Thoracic Society (www.thoracic.org/statements/
index.php)—Includes consensus statements on
classification of idiopathic forms of interstitial lung disease
and disease-specific guidelines on sarcoidosis and
idiopathic pulmonary fibrosis
Pneumotox Online (www.pneumotox.com)—Excellent site
providing information about drug induced lung diseases
Ongoing clinical trials (www.clinicaltrials.
gov)—Involvement in clinical trials will improve our
understanding and management of interstitial lung
diseases. This website provides a useful up to date
summary of ongoing trials
Resources for patients
British Lung Foundation (www.lunguk.org)—Useful site
with links to patient support groups (Breathe Easy groups)
Pulmonary Fibrosis UK (www.pulmonaryfibrosis.org.uk)—
Excellent site including video about pulmonary fibrosis
Pulmonary Fibrosis Foundation (www.pulmonaryfibrosis.
org)—Support group for patients with pulmonary fibrosis in
United States
lung disease.58 However, patients with very early disease
may not have imaging abnormalities. Conversely, some
patients (in particular older people and smokers) may
have parenchymal changes in the absence of clinical or
physiological abnormality.59 60
The main clinical value of high resolution computed
tomography is the identification of interstitial lung disease and the most common variant, idiopathic pulmonary
fibrosis. In an appropriate clinical context, the presence of
classic features of idiopathic pulmonary fibrosis on high
resolution computed tomography allow a confident noninvasive diagnosis without the need for lung biopsy.61 62
However, diagnostic doubt may often remain because of
the considerable overlap between findings in “non-specific interstitial pneumonia” and variants of interstitial
lung disease. In a well conducted retrospective study of
92 patients with biopsy proved interstitial lung disease,
blinded observers made the correct diagnosis from high
resolution computed tomography images in 79% of cases
and identified some features that would favour idiopathic
pulmonary fibrosis over non-specific interstitial pneumonia,63 suggesting that a diagnosis of non-specific interstitial pneumonia will usually require a lung biopsy.64 65
High resolution computed tomography at diagnosis is
valuable in determining prognosis. Several recent studies have shown that patients with features of fibrosis at
diagnosis (including honeycombing and reticular change)
have a worse prognosis and that the extent of lung fibrosis
is a predictor of death.64 66
What is the role of pulmonary function tests?
Pulmonary function tests offer useful information on the
degree of physiological impairment and disease severity, and the results provide a baseline against which
1298
disease progression and response to treatment can be
­measured.
Spirometry is usually done routinely at clinic visits.70
In patients with idiopathic pulmonary fibrosis, a fall in
forced vital capacity of greater than 10% is considered
clinically important, and is associated with a 2.4-fold
increase in risk of mortality.1 71
Transfer factor (also known as diffusing capacity for
carbon monoxide) is measured in pulmonary function
laboratories, and allows a non-invasive assessment of gas
exchange.72 Transfer factor is typically reduced in patients
with interstitial lung disease, secondary to thickening of
the alveolar-capillary barrier impairing gas exchange.
In patients with idiopathic pulmonary fibrosis, serial
measurement of transfer factor can help to clinicians to
estimate prognosis and track progression of disease, and
a change may prompt referral for transplant in suitable
patients; a change in transfer factor of 15% or greater
from baseline is considered clinically important.1 73
Exercise tests may help evaluation of disease severity.76 The six minute walk test records oxygen saturation
before, during, and after exercise and measures the total
distance walked. Some patients with interstitial lung
disease may appear deceptively well at rest, with normal
oximetry and spirometry, but become profoundly hypoxic
when walking.76 Exercise associated oxygen desaturation
significantly correlates with pulmonary hypertension75
and patients who have these features merit more detailed
assessment for pulmonary artery hypertension including echocardiography.77 Substantial oxygen desaturation
(<88%) during a six minute walk test has been associated
with a poor prognosis.78
What is the role of echocardiography?
British Thoracic Society guidelines suggest that pulmonary hypertension should be considered in patients with
interstitial lung disease who have either breathlessness
or lung dysfunction (reduced transfer factor or desaturation on exercise).1 Right heart catheterisation is the gold
standard test for measuring pulmonary artery pressure
but is invasive, and typically transthoracic echocardio­
graphy is performed first.80 81
The prevalence of pulmonary hypertension varies
widely according to the disease and severity of lung
impairment, but is relatively high (30-40%); higher levels are associated with increased mortality.77 For example, in a single centre American study of 88 patients with
idiopathic pulmonary fibrosis who had a trans-thoracic
echocardiograph (allowing estimation of systolic pulmonary artery pressure) within three months of their
initial assessment, the median survival for those with a
systolic pulmonary artery pressure of ≥0 mm Hg to ≤35
mm Hg was 4.8 years, for those with a systolic pulmonary artery pressure >35 mm Hg to ≤50 mm Hg was 4.1
years, and for those with a systolic pulmonary artery pressure >50 mm Hg was 0.7 years.83 Patients with systemic
sclerosis are particularly at increased risk of pulmonary
hypertension (prevalence of 8-12%) and are particularly
likely to develop pulmonary hypertension.84‑86 British
Thoracic Society guidelines advocate annual lung function testing for patients with systemic sclerosis, with
BMJ | 12 june 2010 | Volume 340
CLINICAL REVIEW
bmj.com archive
Previous articles in this
series
ЖЖEvaluation of oral
ulceration in primary care
(BMJ 2010;340:c2639)
ЖЖDiagnosis and
management of the
antiphospholipid syndrome
(BMJ 2010;340:c2541)
ЖЖManagement of seasonal
affective disorder (BMJ
2010;340:c2135)
ЖЖPercutaneous
endoscopic gastrostomy
(PEG) feeding (BMJ
2010;340:c2414)
ЖЖManagement of
medication overuse
headache (BMJ
2010;340:c1305)
e­ chocardiography in patients who have a falling transfer
factor or if the transfer factor is less than 50% of the predicted value.1
Is lung biopsy necessary?
If key radiological features are present (for example, subpleural, basilar, and reticular abnormalities with traction
bronchiectasis and honeycombing in a patient with clinical
features consistent with idiopathic pulmonary fibrosis) the
diagnostic accuracy of computed tomography approaches
90-100% and most clinicians would not opt for surgical
lung biopsy.90 Such biopsies, which are done under general
anaesthetic, are most helpful when clinical and radiological
data result in an uncertain diagnosis or when patients are not
thought to have idiopathic pulmonary fibrosis.61
The site of surgical biopsy is best informed by high resolution computed tomography images of the lung. Video
assisted thoracoscopic surgery is now used routinely rather
than open thoracotomy. Since a range of interstitial patterns
may be seen within the same lung, best practice guidelines
encourage sampling from at least two lobes1 91 and the biopsy
with the pathological pattern associated with the poorest
prognosis should dictate treatment and estimates of disease
prognosis.
Fibreoptic bronchoscopy, which is typically performed as
a day case procedure under local anaesthetic, allows visualisation of proximal airways and sampling of more distal
lung using transbronchial biopsy, and bronchoalveolar lavage to exclude infectious causes.93 It is particularly useful in
sarcoidosis, with diagnostic yields of up to 90%.94 Sampling
of lymph nodes adjacent to the airways via endobronchial
ultrasound guided aspiration is now also possible.95 96 Bronchoscopy with lavage and transbronchial biopsies may be
diagnostic, or increase diagnostic confidence, in other conditions such as cancer, acute pulmonary eosinophilia, cryptogenic organising pneumonia, subacute hypersensitivity
pneumonitis, and some rarer forms of interstitial lung disease
such as alveolar proteinosis.1 However, in most other form
of interstitial lung disease bronchoscopy is not particularly
helpful since the biopsies obtained are too small to make a
confident histopathological diagnosis.
Although lung biopsy will reveal a pathological pattern
the final clinical diagnosis still requires integration of clinical, physiological, and radiological data, ideally by a multidisciplinary team.
Who should manage these patients?
Interstitial lung disease clinics that provide multidisciplinary
care are now common in the UK and elsewhere. This team
approach improves inter-observer agreement, diagnostic
confidence,97 98 and perhaps outcome,99 and this model of
care is advocated in recent guidelines.1 2 Key individuals in
the team typically include chest physicians, pathologists,
radiologists, pulmonary physiologists, thoracic surgeons,
rheumatologists, palliative care specialists, specialist nurses,
and physiotherapists. Multidisciplinary interaction may prevent unnecessary surgical lung biopsies (when the clinical
and radiological impression is consistent with a confident
diagnosis of idiopathic pulmonary fibrosis) and identify
those in whom a biopsy may be helpful. Links with regional
transplant and pulmonary hypertension centres are important and, ideally, patients should have the opportunity to participate in well designed clinical studies where ­available.100
Regardless of the model of care available, the patient’s
g­eneral practitioner and local chest physician remain in­tegral
to providing continuity and quality of ongoing care.
Contributors: OJD conceived the idea for the article and all authors
contributed to the first draft and subsequent revisions. OJD is guarantor.
Funding: No funding was received for this work.
Competing interests: All authors have completed the Unified Competing
Interest form at www.icmje.org/coi_disclosure.pdf (available on request
from the corresponding author) and declare that they have (1) no support
from companies for the submitted work; (2) no relationship with any
companies that might have an interest in the submitted work in the previous
3 years; (3) no spouses, partners, or children with financial relationships that
may be relevant to the submitted work; and (4) no non-financial interests
that may be relevant to the submitted work.
Provenance and peer review: Not commissioned, externally peer reviewed.
Full version and references appear on bmj.com
answers to endgames, p 1311. For long answers go to the Education channel on bmj.com
Statistical question
Multiple significance tests
Answers a, b, c, and d are all true.
On Examination quiz
Postoperative problems
Answer E is correct. Answers A, B, C,
and D are incorrect.
More questions on this topic are
available from www.onexamination.
com/endgames until midnight on
Wednesday.
BMJ | 12 june 2010 | Volume 340 Picture Quiz A is for airway
1 Spirometry was performed, and maximal expiratory and inspiratory flow
volume loops and a flow volume curve were produced. The expected
expiratory curve is shown in black and the patient’s observed expiratory
and inspiratory curves are shown in blue.
2 It shows flattening of the expiratory limb of the flow volume curve
compared with the expected “triangular” shaped curve. This suggests
intrathoracic large airway obstruction. Some flattening of the inspiratory
limb is also seen. The normal expected inspiratory limb should have the
appearance of a semicircle.
3 In view of the patient’s history and examination the most likely diagnosis is
tracheal stenosis secondary to his previous tracheostomy. The differential
diagnosis would include tracheomalacia or central airway obstruction
secondary to malignancy. The patient requires further investigations
including bronchoscopy and a computed tomography scan of his trachea
and chest.
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