According to a scientific study published in the Orphanet Journal of Rare Diseases, a team of researchers were able to identify the mutations responsible for choroideremia in five families of Polish descent. The scientists were able to successfully identify the mutation in all six patients selected for the study, including two mutations that had not previously been associated with choroideremia or any other genetic disorder.
Choroideremia is a genetic disorder which is characterized by gradual loss of vision. As an X-linked recessive condition, it affects males almost exclusively. The disease is caused by mutations of the CHM gene. This gene is responsible for the encoding of Rab escort protein 1; the full disease mechanism is still not completely understood. Symptoms of choroideremia include gradual loss of night vision and peripheral vision. Patients eventually lose their sight somewhere within the range of 50-70 years old. There are currently no real treatments for the disorder, but steps can be taken to slow the progression of vision loss. A diet rich in lutein, omega 3 very long chain fatty acids, fresh fruits, and leafy greens is beneficial. Antioxidant vitamin supplements, UV-blocking sunglasses, and surgery are additional options for management. Gene therapies for the disorder are in development. To learn more about choroideremia, click here.
In the study, six males from five families were selected for testing. They had all been previously diagnosed with choroideremia and received extensive optical examinations to determine the state of their condition. In order to determine the nature of the mutation responsible for each patient, genomic DNA was extracted from blood samples. The researchers used polymerase chain reactions (PCR) in order to amplify the contents of the CHM gene for further analysis. These selected portions of genetic material were then sequenced in their entirety.
New Mutations Identified
The patients were between the ages of 29 and 67, and they all displayed symptoms such a peripheral vision loss and night vision loss that are typical of choroideremia. However, two patients had mutations that had not been described before. Patient 2, a 37 year old male, had a duplication mutation of the nucleotide c.1176dupT. Patient 6, age 52, also had a unique mutation affecting exon 2 c.83C > G. Unlike most other patients, patient 6’s family had no prior history of the disorder. While it can’t be confirmed as the man’s mother was not available for the study, it is possible that is mutation appeared spontaneously.