Female Carriers of X-Linked Inherited Retinal Diseases Want Access to Gene Therapy

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Female carriers of X-linked inherited retinal diseases believe they should have access to gene therapy options to prevent them from passing their gene to their future children, according to new research.¹

Females frequently do not even know they are carriers of the X-linked retinal diseases such as choroideremia and retinitis pigmentosa until after they give birth—and they feel guilty for passing the gene on to their children.²

In a new study, led by Sena Gocuk, a PhD candidate of the department of optometry and vision sciences at University of Melbourne in Victoria, Australia, carriers of X-linked retinal diseases voiced their opinions via a survey on their knowledge of genetic testing, genetic counseling, and gene therapy. Respondents also provided demographic data, genetic testing experiences, and carrier emotions. They lived in either the United States (51%), Australia (19%), or the United Kingdom (14%)—and survey responses differed depending on the country of residence.¹

Survey responses were collected from December 2, 2021 – April 30, 2023. Respondents had to indicate whether they had children and if they knew they were a carrier prior to their pregnancy. In total, the investigators examined 278 responses in the analysis.

On average, respondents in different countries received the carrier diagnosis at different ages.

The mean onset of respondents in Australia was 10 years later than respondents in the United States, marking a statistically significant difference (37 years vs. 27 years, P = .003). Meanwhile, the onset age in the United Kingdom was at 30 years old, which was not statistically significant to the United States (P > .99) or Australia (P = .48).

More than half (56%) of the female carriers had genetic testing and 38% had genetic counseling—many respondents said they had genetic testing because relatives had the X-linked retinal disease gene, so they wanted to see if they were carriers. Respondents also received genetic testing because they were experiencing symptoms related to X-linked inherited retinal disease (20%) and family planning (19%).

Carriers in the United States and Australia had reduced rates of genetic testing (55%) and genetic counseling (36% and 31% respectively), compared to the respondents in the United Kingdom (69% for genetic testing and 46% for genetic counseling). Meanwhile carriers in the United States (40%) were more likely to know about their carrier status before pregnancy than Australia (18%) and the United Kingdom (26%).

“This may explain why female carriers were more likely to know about their carrier status prior to pregnancy in the USA compared to Australia (40% vs. 18%, respectively),” the investigators wrote. “This is important information when considering access to [vitro fertilization]and family planning counselling and supports the need for earlier diagnosis in Australia.”

Many carriers (57%) participated in genetic counselling to gain knowledge about the gene and to see if their child would be put at risk (39%), and 42% of respondents reported genetic counselling was helpful, although 1 in 4 carriers reported receiving no help from a clinician.

In the participant sample, 223 carriers reported giving birth, but only 39% were diagnosed as a carrier before their pregnancy. Yet, 23% reported their carrier status greatly affected their decision to have children. Hence, informing women they carry the retinal disease gene could affect whether they have children or not. If carriers lack this information, they may feel guilty of passing along the gene.

Most carriers experienced feelings of anxiousness (89%), guilt (71%), and concern (91%) for their child, worried they will or had passed along the gene. Also, 52% of carriers worried about their own vision. More than half of respondents (51%) reported that they regretted not going in for genetic testing prior to pregnancy.

According to the survey, respondents (69%) believed that genetic testing was not only for family planning. Also, their healthcare professional had informed them about genetic testing (54%). Though, the knowledge of ocular gene therapy had gaps—only 39% knew that treatment was not administered through the blood stream.

For female carriers who had not given birth (P < .005), had genetic testing (P < .0001), and genetic counseling (P< .001), genetic testing knowledge was significantly greater. But for female carriers who had genetic testing (P <.001), and genetic counseling (P <.0001), genetic counseling knowledge score was greater gene therapy knowledge only expanded in female carriers who had given birth (P < .005).

Overall, 78% of respondents believed that carriers should have access to gene therapy options.

“Carriers were keen to see these options arise—with a large proportion agreeing that gene therapy should be available to them,” the team wrote. “Therefore, researchers should consider including visually symptomatic female carriers in clinical trials of emerging therapeutic options.”

References

1. ^{Gocuk SA, Edwards TL, Jolly JK, Ayton LN. Perspectives of carriers of X-linked retinal diseases on genetic testing and gene therapy: A global survey. Clinical Genetics. 2023;1‐9. doi:10.1111/cge.14442}
2. ^{Dunn NF, Miller R, Griffioen A, Lee CA. Carrier testing in haemophilia a and B: adult carriers' and their partners' experiences and their views on the testing of young females. Haemophilia. 2008;14(3):584-592.}