If a rare disease doesn't affect many people, why should we study it?

Dr Vanessa Sancho-Shimizu

To mark Rare Disease Day 2016, Dr Vanessa Sancho-Shimizu puts forward the case for researching uncommon conditions.

Common sense suggests that a rare disease isn’t going to be particularly common. In Europe it’s defined as a disease or condition affecting fewer than 5 in 10,000 of the general population. In the US rare status is granted when it affects fewer than 200,000 Americans at any one time.

The lack of knowledge and quality information on rare diseases can often result in delayed and incorrect diagnoses. This can result in significant emotional and financial burdens on patients and their relatives.

But when resources are limited, and when the direct impact is potentially so small, how can we justify studying these conditions? Dr Vanessa Sancho-Shimizu, a research fellow working on genetic predisposition to rare childhood infections within Imperial’s Department of Medicine, argues the case from two sides.

“Understanding rare diseases, such as those that I work on, has an understandably huge impact on individual sufferers and their families. It helps give explanations for their conditions, and provides the best hope for identifying appropriate treatments.”

But the impact does not end there. “The knowledge gained from research allows us to not only better understand these rare conditions, but also the factors that underlie them”, says Dr Sancho-Shimizu.

“Determining these genetic factors can help us understand fundamental mechanisms of human susceptibility to disease and infection. This can impact hugely, not only on the people directly affected individual conditions, but at a population level.”

The work recognised by the 2011 Nobel Prize in Physiology or Medicine — awarded for the discovery of the importance of Toll-like receptors in activating innate immunity to pathogens — highlights this. Part of the research into bacterial infections that cause septic shock helped finally identify the sensors of the first line of immune response - something found in all classes of animal and plant life.

“The discoveries of human MYD88 deficiency (which underlies invasive pneumococcal infections) and human TLR3 deficiency (which underlies herpes encephalitis) are examples of this. Both were discovered in Professor Jean-Laurent Casanova’s lab, where I was a postdoctoral researcher”, says Dr Sancho-Shimizu.

The Senior Research Fellow, who joined Imperial in 2012, explains that we are at a privileged and unique point in history for this type of research: “The development of vaccines and antibiotics has allowed people with a variety of single gene defects to survive where they previously would not have, passing their faulty genes on to their children. After three or four generations of this, these genes — whilst still extremely rare — can now be found in those affected more easily.”

“Add to this the development of next-generation sequencing technology that enables us to identify these faults, and we are for the first time able to understand the causes of the kind of infections I work on.”

Dr Sancho-Shimizu’s current research focuses on understanding how individuals’ inherited genetic differences influence the likelihood of various childhood infections. These includes herpes simplex encephalitis — an infection of the central nervous system by the herpes simplex virus, and invasive meningococcal disease — a serious bacterial infection that can cause meningitis and septicaemia.

Dr Sancho-Shimizu has also been a Marie Curie fellow since 2008 and is currently a Medical Research Foundation MRC fellow. Find out more about the Marie Sk?odowska-Curie Actions Reintegration Fellowship in the video below.