In the news
Find related articles on
DNA sequencing used to determine child's treatment
Sources: Forbes, Genetics in Medicine
A 6-year old boy has undergone a life-saving bone marrow transplant following diagnosis by DNA sequencing.
The boy, suffering from an aggressive inflammatory bowel disease, had been through over 100 surgeries over the previous 3 years with very little success. The doctors treating him at the Medical College of Wisconsin had been unable to make a firm diagnosis of his condition, and were thus unable to determine whether a risky bone marrow transplant would be beneficial. They decided to sequence the patient’s exome (the active genes within the genome) in order to search for rare single gene mutations with a frequency lower than 1% in the general population, since more common disorders had been ruled out. They found a mutation in the XIAP gene that had not previously been known to cause the Crohn-like symptoms exhibited by the patient. The sequencing approach they used was not a clinically validated test at the time.
Further tests based on the diagnosis indicated that the boy had a high probability of death if untreated, and this led to the decision to perform the transplant. The child’s parents were counselled for several hours prior to the test being administered, to ensure their awareness of the risks of ‘off target’ or unexpected results, i.e. the uncovering of further conditions that had not thus far been identified. The treatment is reported to have been very effective and the doctors involved say that this is a major step in DNA sequencing’s advancement from a research tool to a clinical one; they point out that the tools used to make the diagnosis were not available when the child first presented 4 years ago. A further 30 patients at the hospital have now been put forward for ‘sequencing treatment’. Clinical applications of exome sequencing capitalising on the increasing speed and affordability of next-generation sequencing are multiplying rapidly (see previous news); the PHG Foundation is currently engaged in a major review of the wider implications of this trend.