FAMILY SUPPORTS X-LINKED RP RESEARCH
AT THE RETINA FOUNDATION OF THE SOUTHWEST

Dallas, TX – (January 2010) – Years ago at the age of 21, Sandy Streur had much more on her mind than the typical college student. Unlike most, the results from a genetic test were far more important to Sandy than any exam grade. Sandy is a member of a family with a long history of X-linked retinitis pigmentosa (RP)— an inherited eye disease that is genetically passed down from a mother to her sons. Betting against the odds, the young Sandy hoped that she did not carry the gene that could rob the sight of her own sons that she would grow to nurture and love one day.

“I was tested myself at U of M [University of Michigan] before I had the kids to find out if I’m actually a carrier,” said Sandy as she thought back on the chain of events that brought her family to be involved in an ongoing research study at the Retina Foundation of the Southwest.

 X-linked RP is a rare, but very aggressive form of RP that is caused by the gradual death of photoreceptor cells responsible for sight. It is called “X-linked” because the disease is caused by a gene defect located on the X chromosome. X-linked diseases affect males and females differently as males have one X and one Y chromosome (XY) and females have two X chromosomes (XX).

Females that carry a faulty copy of this gene (carriers) can transmit it to 50% of their sons and 50% of their daughters. These carrier females may have symptoms of RP that range from very mild to severe. However, when the mutation is transmitted to their sons it results in an aggressive form of RP that can be detected very early in age.

Some have reported to experience changes in their night vision as early as 4-5 years old and loss of their peripheral leading to tunnel vision and legal blindness by 20-30 years of age. Total loss of vision occurs late in life in about 5% of affected individuals.

Currently, there are no treatments available for X-linked RP. However, the researchers at the Retina Foundation of the Southwest are studying the effectiveness and safety of a high dose of a nutrient called docosahexaenoic acid ( DHA) for patients with early-stage X-linked RP. Dr. Dennis Hoffman, the Director of the Pearson Visual Biochemistry Lab, and his fellow researchers believe that DHA is a potential treatment for X-linked RP. They hope that DHA supplementation will slow the progression of the disease allowing those affected to experience a longer period of quality visual function.

The Southwest Eye Registry of the Retina Foundation, led by Dr. Dianna Wheaton, is interested in determining which X-linked RP gene is responsible for causing disease in each family. To date, there are three genes known to cause this disease. Dr. Wheaton is also trying to identify other genes that may influence the behavior of the causative gene, thus, modifying the severity of disease. Gene replacement therapy could eventually target the causative or modifying gene(s) to alter disease progressions in either affected males or carrier females.

With an aging grandfather who went completely blind to RP, a brother and other male relatives who developed the disease, Sandy knew it was possible that she could be carrying a gene mutation that could cause her own sons to lose their vision.

“Justin was a baby, and I don’t think he was even a year old when he was tested at U of M, so Nicholas must have been 3 years old when he was tested. It was quite early,” said Sandy.

Unfortunately, the testing confirmed Sandy’s concerns, and an early diagnosis of X-linked RP for both Nicholas and Justin made it clear that they would experience significant changes in their vision.

“It’s harder to see when it’s dark out, and if things are down on the floor I can’t find them,” said Nicholas who is now 14 years old. Justin, who is now ten years old, also experiences trouble seeing at night. Although, his mother admits he is a little more observant.

“Justin is a little different. He notices things,” said Sandy. “If Nicholas is rushing up the stairs and I’m standing right at the top of the stairs, he’ll run right into me. Justin is a little more observant. Nicholas… no, he’ll knock you right over.”

When the boys arrived to the Retina Foundation in December, they both were due for a long day of visual function tests. Both were clothed in warm sweaters, very appropriate for the blizzard storm they left behind in Michigan only to be greeted by a misty and unusually cold day in Dallas.

They ate breakfast in between the testing and shared quite a bit about their very active lives. “I run cross-country and track. I like to draw, read, write and sing,” said Nicholas.

“I wrestle and play football,” said Justin, and luckily for Nicholas, he practices and competes with the wrestling team at his elementary school instead of making valiant attempts to toss his big brother around.

Although they continuously learn more about the potential to lose their vision to X-linked RP, they choose to focus on being a normal family, supporting one another and enjoying all of the important moments in life.

“It’s not like a tragedy or anything yet. They both see what they’re doing. They can sit down and do their homework,” said Mike, Nicholas and Justin’s step-father. “I guess it’d be different if one of them woke up and their sight was gone one day, but we haven’t run into that yet, so we treat our everyday lives as normal as we can.”

The Streur family is very interested in research for X-linked RP and is excited that the boys are enrolled in the Retina Foundation study that could possibly provide a treatment for their vision. The Streurs have been very active in raising awareness and funds for the DHA clinical trial. The Streur’s raised $3,000 for the Pearson Biochemistry lab by hosting a golf tournament in their home town in Michigan. They join the fight against X-linked RP in hopes that Justin and Nicholas will never have to experience losing their sight.

“A lot of people don’t know about RP. It’s not cancer, or anything like that,” said Sandy. “But we are in a great community. Our neighbors are so hopeful and willing to help in any way. It’s amazing.”

Click here to read more about the Pearson Biochemistry Lab and the ongoing DHA clinical trial.