Medicine’s greatest intellectual challenge may never be solved

Treating a condition requires an understanding of its cause, but many of humanity’s most deadly afflictions remain an enigma to science

For all that medicine has progressed in recent times, the primary cause of most serious illnesses remains unknown.
Whether they be neurological, such as Parkinson’s or motor neurone disease, rheumatological such as rheumatoid arthritis or polymyalgia, dermatological such as psoriasis, gastrointestinal such as Crohn’s and ulcerative colitis, these conditions emerge in patients in a way that we do not yet understand. 
Their symptoms may be alleviated, to a greater or lesser extent, by modern treatments, but the lack of understanding of what accounts for them in the first place is a barrier to any realistic prospect that they may be prevented or cured.   
It is difficult to imagine how different modern medicine would be if we understood the origins of these conditions. But the 40th anniversary this year of the discovery of the role of the bacterium helicobacter in peptic ulcer (and other acid induced stomach ailments) provides a glimpse of what could be achieved were we to trace their causes back to the very root.
Back in the 1950s peptic ulcer was a most grievous illness, its characteristic feature a burning, sickening discomfort in the upper abdomen, fluctuating in severity over many years.
In addition there was a substantial risk of internal bleeding or perforation, leaking the stomach’s contents into the abdominal cavity. Together, these two dire complications accounted for some 10 per cent of all emergency admissions to hospital.
And for this there was nothing that could be done between neutralising the acidic secretions with a bland diet with copious amounts of antacids, or reducing their volume with a major operation that entailed cutting the nerves to the stomach thus allowing the ulcer to heal.
Then in 1984 a 32-year-old Australian doctor, Barry Marshall, swallowed a cocktail containing large numbers of “small, curved bacilli” recently identified as being present  in the stomach wall of patients with the disease. 
Within a week he had become seriously ill with acid induced dyspepsia. He underwent a gastroscopy that revealed the lining of his stomach to be “red and inflamed with bacilli adhering to the surface”. Their eradication with a 10-day course of antibiotics, it subsequently emerged, results in a permanent cure.
Barry Marshall’s paradigm-shifting discovery prompted a major search for other obscure infective organisms that might be the hidden cause of common illnesses. Deploying the now-famous technique of polymerase chain reaction (PCR) that can detect the genetic ‘footprint’ of a virus in infected cells, researchers have demonstrated that both type 1 diabetes and cervical cancer are triggered by a viral infection – respectively coxsackie B and the human papilloma (or wart) virus. And so too multiple sclerosis, reported only last year as being almost certainly instigated by the same virus (Epstein-Barr) also responsible for glandular fever.
For most illnesses, however, the primary cause remains elusive. One might infer some biological agent as yet unknown to science. Time will tell if this last great intellectual challenge in medicine will ever be resolved.  
Finally and further to the recent comments on possible remediable causes of bad breath, my thanks to a couple of readers for passing on their useful observations. 
“I did not realise until well into my adult life that I was intolerant of onions, chives and shallots”, writes one gentleman.
“The halitosis is not of the vegetables themselves but rather a putrid odour that lasts for up to 12 hours.” 
Next, it may be a side effect of commonly prescribed drugs. “Several of my patients taking isosorbide dinitrate for the treatment of angina complained of halitosis”, recalls a retired physician. “This appeared with the onset of therapy, was reversible when it was discontinued and recurred when it was resumed”.  
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