Retinitis Pigmentosa or Choroideremia? Genetic Testing May Be the Only Way to Know

Retinitis Pigmentosa or Choroideremia?

by Mary Hiland

When Retinitis Pigmentosa (RP) was the diagnosis for me at age 18 in 1963, I had already been through a battery of tests throughout the preceding 10 years. There was one test, however, that was not even suggested. Genetic testing was considered only for the sake of curiosity, not for diagnosis. What difference did it make which side of my family passed it down to me? Who cared? Not me. But if I had been offered the opportunity, I would certainly have wanted to find out if I did indeed have RP or something often misdiagnosed as RP called Choroideremia(CHM), which is much easier to pronounce (Choroideremia is a condition characterized by progressive vision loss that mainly affects males. The first symptom of this condition is usually an impairment of night vision or night blindness, which can occur in early childhood). I never heard of this retinal disease because after all, I had not seen a retinal specialist since I was 18, a very long time ago. What would have been the point? I saw an ophthalmologist once or twice, just to have the paperwork signed so I could receive service from the Bureau of Services for the Visually Impaired in Ohio, but I had no interest in looking for another diagnosis. Both my children and their children get regular eye exams, and so far, no sign of RP has made an appearance.

Never Too Old to Learn

Then in casual conversation with the president of the American Council of the Blind of Ohio (ACB), I learned about a conference she had attended about a condition that looks a lot like RP but isn’t. "Why didn’t I hear about this?" I asked, with accusation barely concealed. I should have received some kind of announcement, and I surely would have attended that conference, just for the sake of educating myself and possibly meeting others with the same curiosity. It turns out that a man named Bob Pettipaw, who is currently undergoing genetic testing for CHM did indeed send a letter of invitation, but somehow, I didn’t receive it. Here’s an excerpt from that letter.

Genetic Testing and Clinical Trial for Choroideremia—Letter from Bob Pettipaw

My name is Bob Pettipaw, and I live in West Jordan, Utah. I reached out to ACB-Ohio with the hopes of helping others. I’m 54 now, married with two kids, and I have a retinal degenerative disease called choroideremia—or CHM. It was passed on genetically from my mom, who is a carrier. I’ve passed it on to my daughter, who will probably pass it on to her male children. CHM is similar to many retinal diseases in that it is progressive, meaning it only gets worse. At age 14, my eye doctor told me I had retinitis pigmentosa (RP), and I would be blind by my 40s. I’m sure many of you have a similar story and can relate to my frustration, fears, anger, and hopelessness. I write to you in the hopes that I can shed some light on what I’ve learned in the last couple of years that has changed my life and my outlook.

I was fortunate enough in January of 2016 to be selected for a human clinical trial in Miami, Florida, in which doctors performed a subretinal injection of an engineered virus with replacement genes. The procedure is designed to replace the bad copies of the genes within the cells in the back of the retina, and then the cells start to function properly. The outcome is "advertised" as potentially stopping the progression of the disease. Some patients have improved their vision, and I’m one of them.

Keep in mind, a clinical trial is not open to all. Some retina diseases have progressed too far to treat. Some retinas are too good to treat under current FDA guidelines, so don’t be disappointed if you go through the effort and are not eligible. The key is to get involved to speed the treatment to the commercial market, and your participation makes that possible.

Importance of Genetic Testing by a Reputable Source

I want to stress that unless you are genetically confirmed, you really don’t know what you have. We all want to put our faith in the docs we see and, more often than not, they are right. However, if you are one of the 10 to 20 percent who may be misdiagnosed, you may be missing the opportunity to be part of something that can change your life. I am living proof. I can fill an entire newspaper with the names of my CHM brothers who were misdiagnosed as having RP. Genetic tests are the only way to truly know.

There are a few places where you can have your genetic tests done; my recommendation is to locate a reputable retinal specialist and ask the doctor to confirm your diagnosis through genetic testing. One last note: not all inherited retinal diseases (IRD’s) can be confirmed by genetic testing.

More From My Conversation with Bob Pettipaw

By Mary Hiland

Here are some additional facts that I learned by talking with Bob. Women rarely have CHM. Approximately 99 percent of diagnosed cases are men, but the women are the carriers. Generally speaking, carriers will not exhibit symptoms until late in life. They can, however, pass the gene along to their male children. They could also pass the carrier gene to their daughters, who could then pass the disease to their male children. There is a 50/50 chance of the sons having the disease.

Restorative Clinical Trials

Why have the genetic testing? Mr. Pettipaw explains that current gene therapy requires the patient to be genetically diagnosed. The current clinical trials have shown good results related to stopping the progress of the disease, and in some cases, (20 percent or more) patients have improved their visual function and maintained the gains over years. The current clinical trials are not large, only 40 to 50 people around the world have undergone the therapy, but in approximately 90 percent of the cases, the disease has stopped progressing.

The first study was in Oxford, England, in 2012. Mr. Pettipaw’s gene therapy has been performed at the Bascom Palmer Eye Institute in southern Florida, a reputable medical institute. However, these studies and gene therapies are not cheap. Generally speaking, the sponsors pay for the treatment. In Mr. Pettipaw’s case, travel and lodging expenses came out of his own pocket. Still, he is prepared to pay whatever the price will be if it means there is a chance to maintain or regain his vision. All clinical trials or natural history studies are different regarding what is paid for by the sponsor. Right now, his visual acuity is 20/40 in a very small area in his central vision in his treated eye—improved from 20/70. He describes it as trying to see through a toilet paper or paper towel roll. While many of us who have no vision at all would be glad to have even that much, when you’ve had most of your vision for most of your life, and now both eyes are failing you, you too might consider paying a fortune to keep what vision you have or to regain some.

A major word of caution, not all trials are what they seem. Be sure to read this post on what to look for and how to protect yourself. Another important post to check is the reality and costs of gene therapy.

Learn More About CHM vs RP

Find more information about the latest research on choroideremia.

Read up on what is choroideremia.

Learn about retinitis pigmentosa.

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