Solving the unsolvable

News

The chance of pinpointing the correct diagnosis among thousands of rare diagnoses is not always great. But with a team of experts that can examine our bodies from head to toe and gene by gene, the odds improve significantly.

New DNA sequencing technology is capable of solving cases that until recently were unsolvable.

In Sweden a disease is classified as rare if it is found in no more than 1 in 10,000 people. Meanwhile, there are currently about 8,000 registered rare diseases. Because there are often very few people in any of these diagnosis groups, knowledge about individual diseases is usually concentrated to just a few specialists.

There is also a relatively large group of people who have not received a diagnosis, simply because of the difficulty and complexity involved in establishing one.

"Currently there are people with unclear diagnoses scattered throughout the healthcare system. Patients and family members often have to fight hard for their cause, because combined expertise is necessary to effectively investigate such diagnoses," says Dr. Ann Nordgren, clinical geneticist and project manager at the Center for Rare Diseases at Karolinska. She is also part of the team that works up patients with unclear diagnoses.

It may take years before such patients are correctly diagnosed and some parents of children with an unclear diagnosis simply give up after countless healthcare visits. In many cases chance plays a decisive role in whether patients are adequately worked up.

"I recently met a little girl who had been seen for 156 visits in one year, in many different places by many different experts, before she came to us for comprehensive work-up. With all of these visits the parents could hardly get to work," says Ann Nordgren.

Coordinates specialists to diagnose patients

The Center for Rare Diseases coordinates the specialists to help diagnose patients. An important part of the work-up involves systematic examination of the whole patient, from head to toe. It is common for patients to have different syndromes, often with complicated symptoms such as disproportionate short stature, birth defects and developmental delay.

The team includes specialists in pediatric neurology, pediatric endocrinology, pediatric surgery, clinical genetics, radiology, psychiatry, hand surgery and pediatric surgery, as well as dentists and bioinformaticians.

The team looks closely at small details in the patient's body and appearance. The work-up is often supplemented with radiographic studies. Doctors also look for any genetic patterns for the specific symptoms they are investigating in the family and consider whether anything significant can be noted in the patient's behavior. After all examinations have been completed, targeted genetic analyses are carried out to confirm the diagnosis.

"Cases that ultimately reach us are the very most difficult," says Ann Nordgren. "Nevertheless, we are actually successful in more than half the cases. We can make many diagnoses just by closely examining the patient. Our work is highly specialized, but because we do it all the time, we gain experience. We really have to put two and two together. It's hard to quit before you have the answer."

The Science for Life Laboratory at Karolinska Institutet has high-tech laboratories, with additional potential to find the right diagnosis.

Sequence all 21,000 genes

"That's where we sequence all 21,000 genes for patients who have not been able to be diagnosed through examinations and targeted genetic analysis. In this way, we've begun to solve more unclear diagnoses. Karolinska University Hospital is on the cutting edge of this strategy. We are first in Sweden to offer this opportunity and are extremely proud of it," says Ann Nordgren.

Sequencing is carried out by purifying DNA from a patient blood sample, which is the basis for the analysis. A group of bioinformaticians, molecular biologists and doctors work together to review the extensive analyzed material – gene by gene.

After the review they are likely to have identified some genes that may be of interest for further investigation. In some cases the correct diagnosis can be quickly pinpointed based on a gene, but it is often necessary to further investigate the remaining alternatives.

Everyone has abnormalities in their genes, but most do not affect us. That's why a lot of the genes in the analyzed material have mutations that are of no significance. The challenge is to understand which among all the deviations in the analysis are the cause of disease.

"We look at both where all the various mutations are located in the genes and where they are expressed in the body. We also consider whether this disease-causing genetic mutation can be found in other people around the world.

Among children with unknown syndrome, approximately an additional 30 percent can be diagnosed using this so-called "helix reanalysis," or gene sequencing.

In 1959 there was one known genetic cause of a syndrome – Down's syndrome. Now there are more than 2,000 known genetic causes of syndromes. This figure is sure to increase. At least 80 percent of the approximately 8,000 rare diseases have a genetic cause.

Exciting development

"It's incredibly exciting to be a part of this development. We've been able to identify some new disease genes. Based on one family, for example, we found a mutation in a gene that is important for many functions. As a result we have identified a new syndrome, with mental retardation and skeletal abnormalities, and after our discovery, more cases have been found around the world.

Once a diagnosis is made, we know whether a disease is hereditary, if there is a risk of recurrence in siblings, or if there are other medical conditions that may be associated with the syndrome which may need to be countered or treated.

"It's a relief for patients who have not been diagnosed, despite years of doctor visits, to finally get an answer. We know that providing a diagnosis makes a big difference for the individual and the family," says Ann Nordgren.