In the last 10 years, the medical profession's understanding of rare diseases has improved remarkably says Professor Eugenio Mercuri, a paediatric neurologist with an interest in neuromuscular disorders at Universita Cattolica de Sacro Cuore in Rome. “A decade ago, very little attention was paid to rare diseases,” he says. “Now there is much more awareness about them from drug companies, legislators and others. It's now understood that these types of diseases cannot follow the same regulatory pathways or guidelines that apply to more common disorders, where clinical trials take place with thousands of patients across the world. With rare diseases, we know we have to think about them in a different way.”

Duchenne, for example, is a rare and fatal type of muscular dystrophy that is mainly found in males (and is thought to affect one in every 3,500 boys born globally every year). With this disease, muscles degenerate because of a mutation in the dystrophin gene. It is a severe, progressive and rare genetic condition and boys born with Duchenne have a rapid decline in physical functioning that results in them losing the ability to walk and then permanent wheelchair dependence at around 8-15 years of age. Breathing and heart problems result in people with Duchenne having a shortened life expectancy of around 30 years of age.


Symptoms generally appear in the first few years of life. Sitting, walking and talking can be delayed; then, typically between the ages of 2-5, more obvious signs begin to appear, such as enlarged calves — which cause a waddle when walking — and frequent falling. Diagnosis follows three steps: observing signs and symptoms; blood tests to measure the patient's enzyme levels; and genetic testing.

Eighty per cent of rare diseases have a genetic component, so understanding each patient's gene mutation can be vital. “This helps us to define the disease — and it also helps us inform patients or their families about its progression, treatment and what is known about survival,” says Professor Mercuri.


Early diagnosis and treatment is crucial in the fight against any disease and not simply rare ones. Yet precisely because these diseases are rare, they can be difficult to diagnose. “That's partly because there are so many,” says Professor Mercuri, “and it's very difficult to know them all. Doctors may not recognise their symptoms. Even with 'relatively rare' disorders — such as spinal muscular atrophy and Duchenne muscular dystrophy, for example — a long time can elapse between the first observation by a family doctor and diagnosis. This is why increasing awareness is so very important.”

Professor Mercuri is optimistic about the future, he says, because the mechanism of the diseases in his own field are better understood — and therefore different approaches and treatments have been approved or are in clinical and pre-clinical phases. “There have been times when we had nothing to offer to the families of children with spinal muscular atrophy and duchenne muscular dystrophy,” says Professor Mercuri. “Now, at least, we can inform them of the treatments that have become available — and those that will hopefully become available soon.”

Learn more

Our mission at PTC Therapeutics has always been to build an integrated biopharmaceutical company based on our expertise in RNA biology. We have focused on discovering and developing novel oral treatments for patients with serious and life-limiting disorders. By targeting the processes that modulate RNA biology and affect protein production, we bring an innovative approach to drug discovery. We are focused particularly on the development and commercialization of treatments for rare and neglected disorders.