Key learning points 

  • Interstitial lung disease describes a wide range of conditions, which involve fibrosis or inflammation of the alveolar tissue, affecting gas exchange 
  • The most common types of interstitial lung disease are idiopathic pulmonary fibrosis, sarcoidosis and extrinsic allergic alveolitis 
  • Idiopathic pulmonary fibrosis is often associated with poor prognosis with a mean survival of only three years after diagnosis 
  • There are a range of treatment modalities for idiopathic pulmonary fibrosis including pulmonary rehabilitation and the anti-fibrotic agents: pirfenidone and nintedanib  

Introduction 

It is said in medicine that common things are common, and if you hear hooves, you should think of horses and not zebras. But of course, we will all have patients with less common diseases and so we need to keep the zebra in the back of our mind, or these patients will suffer a delayed diagnosis and thus, a worse outcome. The term interstitial lung disease (ILD) covers a broad range of conditions, all of which involve fibrosis or inflammation of the alveolar wall which hinders gas exchange.1 There are only 2000–4000 new cases of ILD in the UK every year, making it a diagnosis that an average GP may make only once in their career, if at all.1 Nevertheless, it is still important for us to be aware of these diseases as a possibility for patients who present with respiratory symptoms. 

Case study 

Miss P. comes to see you for a review of her asthma. She is a 48-year-old woman who presented last year with shortness of breath, particularly on exertion. She has never been very good at doing a peak flow and so a diagnosis of asthma was made based on the history. She has been using an inhaled steroid inhaler and salbutamol when needed. She is rather fed up as her symptoms seem to be progressing despite regular use of the inhaler. She is short of breath most of the time and has a cough which she just cannot shake. She has had to give up sport and is seriously contemplating whether she will need to have some time off work, as her half hour bus journey with a 15-minute walk at either end is becoming too much for her. She says that she knows you only deal with one problem per appointment, but if there is time, she is worried that she might have a problem with her fingernails and would you mind looking at that as well? 

On examination, you notice that she has widely scattered inspiratory crackles and that her nails are clubbed, a sign that you haven’t seen since medical school. Your antennae start to twitch with the possibility that you may have uncovered a new diagnosis of ILD; it seems that Miss P.’s diagnosis of asthma may not have been all that accurate. You decide to do an urgent referral to your local respiratory clinic, also requesting a chest x-ray and spirometry, the results of which will hopefully be available to them when they see her. A few weeks later you get a letter back which confirms that she has had a CT and has received a diagnosis of idiopathic pulmonary fibrosis (IPF). Miss P. has been given access to pulmonary rehabilitation and the support of a nurse specialist while treatment options are being discussed. 

Discussion 

The most common types of ILD are IPF, sarcoidosis and extrinsic allergic alveolitis.1 Whilst the diagnosis will always be made in secondary care, who will also co-ordinate treatment, there is a lot that we can do for these patients in primary care. IPF is a condition for which the outlook is often poor, with a mean survival of only three years after diagnosis, although 20% will survive for more than 5 years.2 Miss P. is relatively young and works; she may need some support to come to terms with this significant change in her health and the way that she sees herself, as well as signposting to advice about practical issues such as benefits.

There are a variety of treatment modalities that may be used.1 These include oral steroids, immunosuppressant drugs, pulmonary rehabilitation and specific drugs such as the anti-fibrotic agents pirfenidone and nintedanib.1–4 Some patients may be eligible for lung transplantation, and sadly, many will require the principles of palliative care to be used, including strategies to manage shortness of breath at the end of life.2,5 This may include the use of breathing exercises, oxygen, opioids or benzodiazepines.5

Dr Toni Hazell, GP, Somerset Gardens Family Healthcare Centre, London

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