Case study 6: It wears you down

Chronic bronchitis and emphysema

• Occupational history taking/differential diagnosis,
• Occupational asthma.

Our patient has chronic obstructive airways disease, probably now with an acute infective exacerbation.

As you know, people struggle to live a normal life whilst carrying such chronic conditions and part of that normal life is work. Unfortunately, sometimes the work may make things worse.

Quite a lot of women do light assembly work, often part time, in electronic components factories. The work is usually sedentary and not particularly physically demanding. The soldering work involved in the job may invoke exposure to colophony fumes and colophony is a quite common cause of occupational asthma.

The story that has been set out as the clinical issue requires you to make a differential diagnosis. You have to address a quite complex set of issues and try and put them in order:

1. The baseline level of illness associated with the chronic condition,
2. The pattern and severity of the worsening of the patient’s symptoms as they have presented to you just now.

There are quite a lot of possibilities:

• The underlying disease may simply be getting worse,
• There may be an exacerbation due to infection,
• She may have developed asthma,
• All of these things may be happening at around about the same time.

Here, we are going to try and tease out the occupational possibilities.

The diagnosis of occupational asthma depends to a large extent on the examining doctor bearing the possibility in mind. It should always be considered on the development of respiratory disease in adult life but, as it is only a small proportion of asthma (<10%), it is quite often missed especially, as here, when it may be superadded to existing respiratory disease.

An easy way to start thinking down the occupational line is to be aware of some of the common jobs where asthma may be a risk. You have already been introduced to the idea that you should ask a couple of key questions to open this out:

• What job do you do?
• What does that actually entail?

Do you know any jobs where occupational asthma is a risk? Start with the university/hospital setting that you are used to. There is a list at the end of this case study for you to check against and take a note of.

Once your suspicion has been aroused, you have to think about whether the pattern of illness can give you any clues. This is what is called the "temporal relationship" between exposure and illness. Really it is just applied common sense since the exposure, if it is causal, has to precede the illness (or its worsening). Here are some questions you can ask to check this out:

• Were you better at the weekend or when you weren’t working (like on holiday)?
• Does it get worse at work?
• Do you have to take more treatment?

In real life, only a proportion of cases that you encounter fit into simple patterns - what are often described as "classical cases". A lot of cases are much messier and harder to sort out.

In the particular case we are dealing with here the severity of the illness may be due to the interaction of three separately identifiable factors. It's our job to sort these out: as far as the patient is concerned, she is just feeling very poorly! Here is our list:

• The background obstructive lung disease,
• The superadded infection,
• The occupational asthma.

We can get quite a lot of clues from chest imaging and whether or not the patient is febrile. Also the patient may be already used to monitoring her own lung function with a peak flow meter and recording the results. If this is the case, then you can look back to the results before her current illness and try to identify two different things:

• How much worse she has got generally,
• If there are any patterns of worsening and recovery related to work.

With regard to the latter of these points, what would you expect? See: PEFR in occupational asthma (lung function).

A diagnosis of occupational asthma is usually made by observing at least two work-exposure related episodes of worsening and recovery over a four-week period.

When you start investigating your patient, it may all seem quite simple and, because common things commonly occur, it usually is. But our patient has already got quite complicated, with three different aspects of her illness to sort out. Occasionally things get even more complicated and you may have to read the odd newspaper headline along the lines of, "Outbreak of mystery illness kills three: legionella suspected". Other diseases include:

• Reactive airways dysfunction (syndrome),
• Byssinosis (brown lung disease),
• Humidifier fever,
• Legionella,
• Extrinsic allergic alveolitis ("farmers lung" and "bird-fanciers lung").

It's worth just thinking briefly about what sort of team you would get together to track down a "mystery illness" and how you would study it.

Common jobs where there may be a risk of occupational asthma:

• Soldering (electronics, hobby),
• Bakery work,
• Drug manufacture,
• Hospitals - use of gluteraldehyde and other aldehydes,
• Animal studies in research institutions,
• Spray-painting.