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• please explain,...
• Posted: 2008-03-09 08:55:02 By Patience T
• I have RP, my parents and sibings dont. My husband does not have it...my question is what are the stistics in this case, which I know many people have been in. I have 2 children and one on the way, what are the odds of my children being affected. I know nothing is in concrete but Im just curious as to typical odds.
  
  Thank you

• Re: please explain,...
• Posted: 2008-03-09 15:33:44 By Darran Z
• Read the publication "Inheritance Patterns of Retinal Degeneration" under Publications. This explains the three main inheritance patters (Autosomal Recessive, Autosomal Dominant and X-linked). Family histories of RP will be Autosomal Dominant and X-linked. It sounds to me like you have autosomal recessive, which in this case, none of your children will have RP. The reason why you have it is, that we recieve two genes from our parents (one from each). They were carriers of the RP gene mutation. They don't exhibit RP because the dominant gene paried with the recessive gene is a stronger influence, thus, RP isn't exhibited. You happened to be the one who recieved both recessive, mutated gene from each parent, thus having RP. You're children will be carriers of RP but not be affected by RP.
  
  So let's look back at Mendelian inheritance pundent square (from middle school science) I can show how you got RP.
  
  Let's let "A" represent a dominant non-RP gene and "b" the recessive RP gene. So your parents had the Ab match up.
  
  A b
  A AA Ab
  b Ab bb
  
  Thus 1 of 4 chance of no RP (AA), 50 percent change of continuing a carrier RP (Ab) and 1 in 4 chance of getting RP (bb). Because these are the only chances and possible ways to pass on genes. So your siblings coulc be carriers or could be non-RP carriers.
  
  You can repeat the process of yourself to see that all your children will be RP carriers by replacing one (horizontal or vertial) Ab tiwh bb. Then for your hubby, if he is not an RP carrier, AA. Then you see all yoru children will be carriers but not affected.
  
  Now the process continues for yoru grandchildren. At the generation of yoru grandchildren the RP coudl be stopped at it's tracks as it will be a 50-50 chance of continuing. This is why people with Autosomal Recessive inheritance form of RP have no family history.
  
  Darran

• Re: please explain,...
• Posted: 2008-03-09 21:03:55 By Kim V
• Hi,
  
  Darren gave an excellent explaination of recessive rp, that is what I have, there is no family history of RP, my maternal grandmother had macular degeneration, but no rp as far as the "eyes can see" so I am definitly the lucky one in our family, and I too have 3 little boys and was very concerned for them but now understand that as long as my husband is not a carrier, my children are simply going to carry on the recessive gene, and hope that they do not marry anyone with the recessive gene too and we can stop this thing in our family (god willing). Enjoy your baby on the way, and a friendly word of advise, plan for the fourth, 3 is an odd number!!!!:) I have a 4 yr old and twins that are 2. Take care and good luck...Kim

• Re: Re: please explain,...
• Posted: 2008-03-09 23:20:51 By Carol C
• Not to muddy the waters, but... my brother's X-linked cone-rod dystrophy (classified one of RP's- also technically a macular degeneration that eventually involves the entire retina) would have looked recessive to us as well as no one in our line had this ( except my mother's sister eventually went blind with "retinal degeneration, unspecified" which seemed to be typical macular degeneration- loss of central vision, would turn her head to look at fridge contents, etc.). She had visual problems all her life that gradually progressed ( not completely impaired until her 60's- my grandmother, caring for self at age 81, blind at death age 91)), but because it was not the typical tunnel vision of RP, no one guessed this could be it- plus, detection tests were just not as good as now. Her mother had an uncle with same problems, and a first cousin, then later generations as well(first RP diagnosis 1979). If we did not know all these distant relatives, we would not know it was X-linked ( aunt had no bio kids, only brother and only maternal uncle uneffected- small family). My mother died age 69 with no symptoms that we could tell, yet was just as much a carrier as her sister. Many people have no knowledge at all of great-great uncles, etc.My point: could you be an effected carrier of the X-linked form? I say this because my brother's sample was used to make a DNA test for any relatives of his. Their samples can be checked for this same mutation. This test took about 3 months for them to make. His mutation is in a "hotspot" for XLRP mutations, called RPGR ORF15. Because they only have to look there, it's quicker than scanning the whole gene ( would take years, I think). If you carried a mutation there, why couldn't they make a test for you as well? Then, your boys could be checked, and know for sure. You would have 2 X's to scan ( being female). This test only cost $350 to us, anyway, I'm sure many costs were obsorbed by the research. Seemed cheap to us to find this out!!! I had the test, I do not carry the mutation, my results took only a month to get back( I'm female, with 2 X's to scan). A 4th cousin (effected male) had it, carries exact mutation ( of course, he would). Contact me at ectjcarlson@aol.com, if you like. Carol C.

• Re: Re: Re: please explain,...
• Posted: 2008-03-10 00:19:52 By Darran Z
• Carol,
  
  This is why I stated the three main inheritance patterns. There is room for complexities as one learns about this. Even speaking with a genetic counselor they would make the same assumption based upon what information is known and make correction as more information becomes available.
  
  It is not to state that those who are of the other two forms (Dominant or XLRP) are not the start of a new mutation. New mutations of dominant as I have read are more mild and not as aggressive. One can safely rule out XLRP in this particular situation with no knon history and the fact that Patient is female. That is almost next to impossible without a family history of XLRP.
  
  There are some rare forms of RP, one called Mitocondrial RP which the mitocondrion of the cells are defunct. This is even more rare than the three main inheritance forms.
  
  And true, many CRD forms of RP are often diagnosed as a macular degenerative disease. That form of RP can be classified in either as a juvenile macular degeneration or RP, depending who you speak with.
  
  Darran

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 11:22:31 By Kim V
• Thanks Darren for your excellent explaination, I actually had the same question but there is not a single case of anything other than my grams macular degeneration in our family history. She was not affected by this until she was well into her 70's. Talking with drs etc. and the team of specialists that I saw many yrs ago, I definitly have the recessive form of rp, dna testing is not out of the question but in light of the fact that my brother, cousins and their children are all unaffected, it seems highly unlikely that my children will have a problem, carriers but not affected. Well anyway, great explanation and you are excellent at presenting the material...Thanks...Kim

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:19 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:20 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:25 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:26 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:26 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:27 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:28 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:33 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:33 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:33 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:34 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:35 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:39 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:41 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:42 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:47 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:47 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:47 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:52 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:52 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:53 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:13:54 By Carol C
• Hi, Darren!
  
  

• Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 13:23:11 By Carol C
• Sorry about those earlier posts! Have no idea what happened- must have hit a weird button. I repositioned my keyboard- big mistake, I guess. Is it possible to erase them??? Anyway, Hi, Darren!
  
  Can we truly rule out XLRP in this case? That was my point about my aunt- she was nearly as effected as any male, yet was a female carrier, and if we did not know about all our distant relatives, she would look autosomal recessive, as both her only brother and only maternal uncle were uneffected ( fortunate in the 50/50 chance arena). Yet, due to DNA testing, we know psitively that our mutation came down on the X chromosome. Carol

• Re: Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 14:22:27 By Darran Z
• I wasn't talking about your family's situation but rather Patience's situation. Since there are no knowns, including distant relatives. Your family would be different since you indicated distant relatives being affected. That is the key here.
  
  Darran

• Re: Re: Re: Re: Re: Re: please explain,...
• Posted: 2008-03-10 15:09:40 By Carol C
• I was talking about BOTH Patience and Kim's situations, both looking like isolated recessive cases, and maybe are. But my aunt's situation looked that way, too. Possibly both these women just don't know enough about their genealogy to know it's X-linked, as most people do not know their distant relatives, and X-linked can be passed on for many generations through females only, some of these carriers being completely unsymptomatic, like my own mother.

• Re: Re: Re: Re: Re: Re: Re: please explain,...
• Posted: 2008-03-11 13:50:09 By Darran Z
• Carol,
  
  You are missing my whole point. I stated that this would generally be the concensus UNTIL FURTHER INFORMATION IS REVEALED. What is wrong with that?
  
  Genetics is complex, I'll admit to that. But the starting point is at the three main inheritance modes at the surface. Until further investigation is done (i.e. genetic testing or further inquiry of distant relatives) they will start and presume with the three main inheritance patterns. That's the starting point when trying to work your way through genetics.
  
  Darran

• Re: Re: Re: Re: Re: Re: Re: Re: please explain,...
• Posted: 2008-03-12 09:56:55 By Carol C
• Darren, my EXCITING point ( I think, anyway), is that there IS genetic testing available!! My brother submitted a blood sample in July, mutation found in October, and available to relatives! But this is because it's on the X, and in a known location on the X, so they only had to look there.This is a HOTSPOT for XLRP mutations, and many people are being found to be XL who were thought to be recessive ( more recent statisitics give higher % of RP being XL). It was only $350 to learn this. Not knowing the ages of these women in these posts, my XLCRD-carrier aunt was effected with symptoms herself IN COLLEGE, so the assumption would have been made that she was dominant or recessive, except no one knew anything about this then- 1940's ( so she had to live with family assumptions that she was "slow" and couldn't keep up with reading assignments for that reason). My aunt had NO siblings and NO first cousins who were effected, and NO bio children (adopted kids), but it was a small family ( only one brother and one sister, only one maternal uncle and 2 male cousins through him, her sister much younger, and only long line of female children until my brother in 1970). They knew a g-uncle with vision problems, and grandma's cousin became blind, but it's been SINCE THEN that we have known about the further generations with many cases. Now, people don't have to wait for all this family history to develop. If I had started having children in 1976, it would have been TOTALLY IGNORANT of this family history. Carol

• Re: Re: Re: Re: Re: Re: Re: Re: Re: please explain,...
• Posted: 2008-03-12 13:16:25 By Darran Z
• This is why I stated "until additional information is known." Testing is up to the individual. That can and will confirm an inheritance pattern.
  
  Although, I would caution that not every form of RP known is testable. As it stands, only X-linked RP and a few of the dominant forms are testable. The rest, is generally done on a research basis. Depending who does it, will often depend whether the results are known and sent back to the patient.
  
  Darran

• Re: please explain,...
• Posted: 2008-03-09 21:09:53 By Kim V
• Hi,
  
  Darren gave an excellent explaination of recessive rp, that is what I have, there is no family history of RP, my maternal grandmother had macular degeneration, but no rp as far as the "eyes can see" so I am definitly the lucky one in our family, and I too have 3 little boys and was very concerned for them but now understand that as long as my husband is not a carrier, my children are simply going to carry on the recessive gene, and hope that they do not marry anyone with the recessive gene too and we can stop this thing in our family (god willing). Enjoy your baby on the way, and a friendly word of advise, plan for the fourth, 3 is an odd number!!!!:) I have a 4 yr old and twins that are 2. Take care and good luck...Kim