Dr. Sheila Riazi
Dr. Sheila Riazi, Associate Professor of Anesthesia at U of T and Medical Director of the Malignant Hyperthermia Investigation Unit at UHN, received US$2.7 million in funding from the National Institutes of Health in the United States to advance treatment for malignant hyperthermia. (Photo: Courtesy Dr. Sheila Riazi)

Malignant hyperthermia (MH) is one of the most dangerous disorders you have never heard of – but Dr. Sheila Riazi is looking to change that.

Along with her research collaborators, Dr. Riazi — an Associate Professor of Anesthesia at the University of Toronto and Medical Director of UHN's Malignant Hyperthermia Investigation Unit (MHIU) at Toronto General Hospital — has received US$2.7 million in funding by the National Institutes of Health (NIH) in the United States for their research on MH.

MH is a rare genetic disorder that causes a fast rise in body temperature and severe muscle contractions after receiving general anesthesia. However, the disorder is usually only discovered when a patient receives anesthesia during surgery, and if left untreated it can lead to serious complications such as kidney failure, breakdown of muscle tissue and even death.

"A unique challenge with MH is its variable penetrance, which means you may have no problems your first time getting anesthetic, but may have a reaction on your third or fourth time," says Dr. Riazi, who is also a staff anesthesiologist at Toronto Western Hospital (TWH). "This makes the predictability of this disorder much harder."

While the incidence of MH is approximately one in 10,000, the gene which causes the disorder is much more common, with one in 400 people being carriers. Luckily, treatment is available through a medicine called dantrolene, a potent muscle relaxant.

However, Dr. Riazi believes MH as we know it is only the tip of the iceberg.

Through her research, Dr. Riazi is challenging the concept of MH as solely an anesthetic-induced disease. Her experience has shown that a significant portion of her patients who are susceptible to MH – two-thirds, in fact – have existing muscle problems that are triggered by other factors, not just anesthetic.

Plan is to 'define this disorder more clearly'

Characterized as "HH," these patients experience severe cramping and muscle breakdown when exposed to heat, certain medications, viruses and even exercise. This means many patients susceptible to malignant hyperthermia are more likely to have HH. 

"We think HH is part of the spectrum of the same disease as MH," says Dr. Riazi. "The details haven't been well characterized yet, but our plan [through this grant] is to define this disorder more clearly."

While MH can affect anyone regardless of age or gender, HH is unusual in that it tends to affect an unexpected portion of the population – people who are fit with a lot of muscle mass.

As a result, Dr. Riazi often treats young, athletic patients who are otherwise the picture of health, but can be quickly debilitated by something as unassuming as the common cold.

And unlike MH, there is no available treatment for HH, making the funding award even more significant.

"The biggest obstacle is that rare disorders like this are often very difficult to get funding for," says Dr. Riazi. "[This grant] will help us find solutions – and if we succeed, it will be a huge help to patients."

The funding will help Dr. Riazi and her collaborators understand the pathophysiology – the functional changes – of the disease better and develop treatment based on those findings.

When asked what motivates her research, Dr. Riazi immediately emphasized her patients. "Our patients are amazing," she says. "They are always so co-operative and grateful."

As the only centre in Canada for MH research, the MHIU sees the largest number of MH patients in North America. Dr. Riazi's patients often come to the MHIU feeling like they have no solutions after being misdiagnosed with other disorders such as fibromyalgia or chronic pain.

At UHN, they feel that much closer to a solution.

"Unless we learn more about this disorder, we cannot help [these patients]," Dr. Riazi stresses. "That's why it's so important to find a solution – it will have a major impact." ​

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