ausdoc . |
com . au |
|
16
X MONTH JUNE library at www . ausdoc . com . au / therapy-update
|
2022
2023
|
BMJ 2022 ; 377 : e068645 . |
||||||
|
confirms multiple well-circumscribed nodules in the mid to upper zones between 2-7mm in diameter .
Sam is discharged home pain and symptom free . He is referred to a respiratory physician as an outpatient and undergoes pulmonary function tests , which are within normal limits .
The specialist diagnoses chronic silicosis . It is thought the chest pain was a coincidental presenting symptom .
Discussion
Silicosis describes a group of respiratory diseases caused by inhalation of free crystalline silica , often from occupational exposure . Common industries associated with workplace exposure include mining and hydraulic fracturing , sandblasting , foundry work , masonry and stone cutting .
Silicosis can be grouped by acuity , into acute , chronic silicosis or accelerated disease .
Chronic silicosis is the most common form and is the basis for this discussion . This condition develops 10-30 years after exposure . 1 It manifests as simple silicosis and / or progressive massive fibrosis ( PMF ).
Simple silicosis describes multiple small (< 10mm in diameter ) nodules in the upper lung zones . 2 These can be symmetrically or asymmetrically distributed and can be well-rounded or irregular .
PMF , also known as conglomerate silicosis , occurs when these nodules coalesce . PMF is associated with hilar lymphadenopathy with calcification in 5 % of cases . 2 Emphysematous changes occur in the lower lobes secondary to fibrotic retraction in the upper lobes . 2 PMF can be asymmetrical and cavitation may also be present in mycobacterial superinfection or in advanced disease . This often also renders exclusion of malignancy difficult .
Chronic silicosis can be diagnosed clinically in those with a history of silica exposure and a disease-free period following time of first exposure . Diagnosis can be made with history alongside chest imaging consistent with silicosis , following exclusion of alternative diagnosis . There is generally no need for tissue biopsy
|
or bronchoalveolar lavage , unless it is felt necessary to exclude an alternative diagnosis .
Silicosis typically exhibits few signs on examination . Only 25 % of those with simple silicosis will have adventitious sounds on auscultation . 3
It should also be noted that clubbing is not commonly associated with silicosis and should prompt investigation of alternative diagnoses .
There are no specific blood tests to diagnose silicosis . Bloods can be used to exclude alternative pathology or to monitor for complications such as superimposed mycobacterial infection .
High-resolution CT is not typically necessary in simple silicosis unless there are atypical clinical findings or suspicious outlier nodules on CT . In the instance of complicated silicosis , high-resolution CT is preferred over chest X-ray for evaluation of confluent nodules or emphysematous changes as seen in PMF .
Referral for pulmonary function testing is crucial to evaluate airflow impairment in the context of abnormal imaging . A broad range of results can be seen — from no abnormalities to severe airflow impairment . Generally , in cases associated with abnormal pulmonary function tests , this will typically demonstrate a mixed picture of obstructive and restrictive ventilatory impairment with decreased FEV 1 and FEV 1 / forced vital capacity ratio . 5
There is no recommended treatment for chronic silicosis . Management is centred around limiting further exposure to inhaled silica , optimising respiratory function and treating any airflow limitations . Smoking cessation counselling is essential as cigarette smoking accelerates progression of chronic silicosis . 4 Long- and short-acting bronchodilators are recommended if there are any reversible obstructive deficits on peak flow rate assessment . Routine vaccinations for respiratory infections are warranted , including annual influenza vaccination and pneumococcal and COVID-19 vaccination according to schedule recommendations . Workplace compensation may be applicable in relevant cases .
References on request from kate . kelso @ adg . com . au
|
The patient denied shortness of breath , cough , palpitations or other cardiac symptoms .
Have an interesting clinical case ?
Earn CPD points by preparing educational content for publication .
We pay $ 400 for each published case .
For details , email medical co-editor kate . kelso @ adg . com . au
|
What is the most likely diagnosis ?
a Non – small cell lung cancer
b Foreign body aspiration
c Psittacosis
d Infective exacerbation of bronchiectasis
Have an interesting spot diagnosis ?
Earn CPD points by preparing educational content for publication .
We pay $ 100 for each published quiz .
For details , email medical co-editor kate . kelso @ adg . com . au
ANSWER The answer is c . The CT scan demonstrates consolidation and an air bronchogram in the inferior lobe of the right lung . Infection , bronchial obstruction , malignancy and haemorrhage may all account for these CT features . 1 In the setting of infective symptoms , with clinical features suggestive of atypical pneumonia ( dry cough , normal white cell count with elevated CRP , extrapulmonary features , poor response to amoxycillin ) and recent exposure to unwell chickens , psittacosis is the most likely cause . Other clinical features that favour this diagnosis include lobar consolidation and a relatively low heart rate in the setting of temperature over 40 ° C . Highly pathogenic avian influenza also warrants consideration in the setting of exposure to unwell birds , although lobar consolidation is less commonly seen with viral pneumonia . 1 , 2
Psittacosis is a zoonotic infection caused by Chlamydia psittaci : a gram-negative bacterium . Birds are the major reservoir , with C . psittaci documented in more than 450 species of birds globally . 3 Most infections are contracted through aerosol exposure to feather dust or dried faeces of pet or wild psittacine birds — such as lorikeets , budgerigars and cockatoos — or poultry . 1-3 Rare cases of human-to-human transmission have also been reported . 2 The incubation period is typically 5-14 days . 3
Disease severity varies from asymptomatic to significant multisystem involvement . High fever , headache and dry cough are common , and extrapulmonary symptoms are often present , including gastrointestinal ( nausea , vomiting , haemorrhage ) and neurological symptoms ( dizziness , headache , altered consciousness ). 2
The diagnosis is confirmed via PCR for C . psittaci from nasopharangeal swabs , sputum or bronchoalveolar lavage or through a fourfold rise in antibody titre on acute and convalescent serology . 2 , 3
Recommended treatment is oral doxycycline , azithromycin or clarithromycin . 4 Dr Kate Kelso is a GP and medical editor at Australian Doctor .
References on request from kate . kelso @ adg . com . au
|