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Wednesday, August 19, 2015

Nature's Human Disease Arsenal

"I had to be tube fed, suctioned all the time. And my body was literally just wasting away. I would not wish it on my worst enemy."
"It is such a devastating illness and the journey is so lonely, and you never really come back to the person you were."
Sonia Whyte-Croasdaile, nurse/social worker, post toxic epidermal necrolysis
Peter J. Thompson/National Post
Peter J. Thompson/National    PostSonia Whyte-Croasdaile, a survivor of toxic epidermal necrolysis, at her Milton home. Four years later, She is still suffering the debilitating after-effects of the disease.
"This is a travesty [not pre-testing patients for TEN...toxic epidermal necrolysis]. It's the kind of thing that when I started doing research in this 30 years ago, we prayed would exist: to be able to screen people, and not give drugs to the wrong people.... Why there are blinders on about this, I do not understand."
"We've got good science, we've got good ways of preventing something, but [in Canada] we don't have the cohesiveness or the focus."
Dr. Neil Shear, head, drug-safety clinic, Synnybrook Health Sciences Centre, Toronto

"It's not very well known, to be honest with you. In our dermatology community, guys don't screen for it and don't recognize it [toxic epidermal necrolysis]."
Bruce Carleton, head, pharmaceutical outcomes program, British Columbia Children's Hospital
The skin condition named toxic epidermal necrolysis is triggered generally by allergic reactions to prescription drugs. As such, it should be preventable, if care is taken to test patients before prescribing drugs, particularly those known to be implicated in causing TEN in some susceptible people. According to Dr. Carleton, a "perfect storm" inclusive of genetics, drugs and health condition appears to trigger TEN.

There are dozens of drugs suspected of having the facility to trigger toxic epidermal necrolysis. The list includes common sulpha antibiotics. The connections of some drugs with those genetically predisposed to TEN have been studied, and according to Dr Shear, tests in these instances should be automatic, to prevent TEN onset. Particularly susceptible are people of Han Chinese, southeast Asian or South Asian heritage.

The drug allopurinol, prescribed for gout and other diseases, for example, should only be taken by patients who have been pre-tested. Those tests have been available for at least six years; their cost ranging from $100 to $200 per test, and their application capable of preventing up to 70 percent of cases of TEN. Wide use of the test could result in far fewer people presenting with the dread skin disease.

The label for allopurinol, for example, makes clear that there is a known link between a specific HLA gene and TEN, while going on to state that the value of screening for the gene "has not been established". Ms. Whyte-Croasdaile, 47, was stricken with TEN, acquiring burn-like blisters on her body. Her state progressed to the point where she was almost incapable of swallowing, was almost blind, and was hospitalized for six weeks.

Four years after her recovery, debilitating after-effects of the disease continue to blight her existence. She had to regrow her eyebrows, eyelashes and toenails. She had to learn to walk again, and was able to eat only baby food for a while. Her mucous membranes were damaged to the extent that she no longer produces saliva, so eating is difficult, and her congenitally dry eyes are constantly irritated.

Peter J. Thompson/National Post
Peter J. Thompson/National Post    Sonia Whyte-Croasdaile holds a photo of herself in hospital while she was suffering from toxic epidermal necrolysis.

Because it is not routine to test patients for their genetic susceptibility to acquiring toxic epidermal necrolysis before drugs are prescribed in this risk group, people are succumbing to the disease, and suffering its consequences. And they are dire, including death. In Singapore, health authorities urged doctors to test patients for a specific gene before prescribing the epilepsy drug carbamazepine. That resulted in a huge reduction in the incidence of TEN, or that of the less severe Stevens-Johnson syndrome.

TEN's early onset symptoms are readily mistaken for those of influenza. And then the skin begins to blister and peel, painful lesions spreading across the entire body, invading the mouth and throat, damaging mucous membranes. The large, open sores that are produced become prone to infection which can lead to sepsis, organ failure and ultimately death.

Over the ten years ended March 2012 a study identified 141 cases of TEN and 567 of Stevens-Johnson disease in Ontario. Of that number 127 people died in hospital or in two months of their release from hospital. Of the TEN patients 23 percent died.

The burn unit at Edmonton's University of Alberta Hospital typically sees between three to ten cases annually of TEN. Plastic surgeon Dr. Ted Tredget recalls a few years back treating two patients with the disease at the same time.

Several DNA variations involving "HLA" genes that are linked to TEN have been identified which are capable of predisposing people to the reaction as a result of using specific medications. Advances in genomics have benefited in acquiring new knowledge about this dreadful disease.

Now, the issue is convincing federal and provincial regulators and the pharmaceutical industry to agree that routine genetic screening before administering certain drugs should be a recommended proactive course of action.

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