Researchers have identified a new human disease—”combined immunoficiency” or CID—and the gene responsible for it, “ICOSLG.”
The disease is characterized by a weakened immune system and, because of the body’s lower ability to fight off infections, patients are susceptible to recurrent life-threatening infections, such as pneumonias, and debilitating infections, such as progressive warts.
The discovery, published in the Journal of Experimental Medicine, originated with the medical investigation of a 36-year-old male patient who had endured recurrent sinusitis and pneumonias, yeast infections, and viral infections since childhood.
“We are so relieved to finally receive a diagnosis…”
Researchers used a state-of-the-art technique called whole exome sequencing to evaluate the patient’s genes and analyze his genes compared to those of his family members, in order to identify the abnormal gene that was responsible for his disease.
“This discovery will help patients who have escaped diagnosis to now be correctly diagnosed,” says Donald Vinh, a researcher from the Infectious Diseases and Immunity in Global Health Program of the Research Institute of the McGill University Health Centre and an associate professor in the Division of Infectious Diseases at McGill University.
“By doing so, patients could benefit from aggressive monitoring of potential complications and earlier implementation of tailored therapies. Pinpointing this gene will also help scientists identify who else in the family is at risk, including newborn babies before they become sick.”
“We are so relieved to finally receive a diagnosis, after so many years of doctors not knowing what was wrong with me, and with the research providing the potential for eventual treatment for me. And knowing that our children are not affected is a major comfort,” says the French-Canadian patient, who resides in Eastern Québec with his wife and two young children.
The scientist says an additional benefit of the discovery is a glimpse into whether it causes the immune deficiency that occurs as people with Down syndrome age.
“This gene is on Chromosome 21 and it turns out that Down syndrome’s patients, who have three Chromosomes of 21 (instead of the usual two), have a similar problem with their immune system. We’re looking to see if this causes the immune deficiency reported in adults with Down’s syndrome,” says Vinh, whose study of genetic defects of the immune system has fueled his “medical detective” reputation.
A famous case
“At the clinical level, previous evaluations did not look at all his symptoms in their entirety as one disease but as individual and unrelated problems. But once you start putting the abnormalities together, you see our patient’s case was similar to that of “Bubble Boy,” which was the most severe form.
“Our patient’s disease is in the same family of conditions but because he was an adult, nobody thought to explore this possibility,” says Vinh, who explains the “Bubble Boy” name was given to a young child named David Vetter in the 1970s, whose severely weakened immune system required him to live in a sterile bubble from birth.
“Once we related our patient to the Bubble Boy’s disease, which we know is genetic, we discovered this new gene,” says Vinh.
Vinh has already received numerous requests from physicians around the world to test patients who may have the same medical condition diagnosed in his own patient, providing hope for both patients and their families.
Funding came from La Fondation du Grand Défi Pierre Lavoie, Fonds de Recherche du Québec – Santé, RI-MUHC, Canadian Institutes of Health Research, Bristol-Myers Squibb, McGill University, and CSL Behring Canada.
Source: McGill University