Non tuberculous mycobacterial disease

A couple of weeks off and a new baby in the house have had an impact on my ability to put together a cohesive spiel for the month. There are a couple of things on my mind though.

Non tuberculous mycobacterial disease was a topic of an editorial in a copy of the American Journal of Respiratory and Critical Care Medicine from late last year which was recently brought to my attention again. A case series of 63 patients with pulmonary NTM infection in Canada was reported, with a view to finding if there is a particular type of patient who is at risk of this problem. To cut a long article short, patients with pulmonary non-tuberculous mycobacterial infection were overwhelmingly female (95%) and, compared to ‘age and ethnicity matched’ control subjects, taller, leaner with higher rates of scoliosis, pectus excavatum, mitral stenosis and mutations in the systic fibrosis transmembrane conductance regulator.

The accompanying editorial alludes to the ‘Lady Windermere syndrome’ (‘too fastidious to cough effectively’), although an unwillingness to cough was not evident in the patient cohort – and is not evident in my waiting room. Interesting epidemiological points were made:

- around 20 to 40% of pulmonary non-tuberculous mycobacterial isolates are associated with clinical disease

- patients with pulmonary NTM disease usually are diagnosed only after long periods of illness

- drug therapy last for usually around 18 months – much longer than for TB

- recurrence requiring treatment after a lengthy treatment course approximates a rate of 50%

In Ontario, Canada – and I apologise for a lack of local data – the rate of isolation of NTM in the lab is increasing at a rate of 8% per year (as opposed to TB – falling at a rate of 4% per year). The editorial finishes with the following statement ‘ cases of NTM lung disease are no longer just ‘curiosities’ but may well be the leading edge of a major public health problem. The time for action is now’.

With the passing of one of my patients due to idiopathic pulmonary fibrosis it might be worth stating that there is no particularly bright light on the horizon in regard to treatment of this condition. Accurate information at the outset of the disease is vitally important. The information brochure available on our website for interstitial lung disease may be of some benefit, but there is no getting away from the complexities involved in trying to understand the clinical behaviour of this and other interstitial diseases. Once the diagnosis of idiopathic pulmonary fibrosis* is clarified patients still may experience either;

- prolonged stability over years

- progressive and relentless deterioration

- sudden and acute decline.

The textbooks don’t really allow for the first of those options, and stability is certainly the exception. I have, however, seen patients stable over 2 years or more even with a confirmed diagnosis of IPF. I don’t think all of these patients who exhibit some stability have a different diagnosis, as is often argued in the literature and as has historically been the case. Confident prognostication at the outset is, however, largely unhelpful. Nevertheless, patients need to be ready for deterioration and ultimately death.

The ‘best’ treatments we have are of no proven benefit. Our palliative care systems don’t always support patients with non-cancer terminal conditions as well as patients with cancer. Palliation of dyspnoea is difficult.

My patients often tell me, with palpable relief, when the diagnosis of IPF is made, that ‘at least it’s not cancer’. I used to be a little more hesitant than I now am at replying that it may as well be.

* it is very important not to impart the same prognostic advice to patients with interstitial lung disease associated with connective tissue syndromes as I have outlined above.