Is Tamum or another geneticist there please? I have a question Re: Ocular Albinism

[Lulabell]

Hi,

I've posted for some advice on this and it's been suggested that there may be a geneticist who could help.

My partner has ocular albinism and answers all my questions about it but is very sketchy on the genetic aspect. He knows that it could be passed onto his children, but that's about it. I am hoping to start a family in the next few years and I know this is a major concern for him (although he deals with it perfectly well himself), so I've been trying to find the info myself. All the articles I can find online only deal with the actual effects or diagnosis etc, and dont talk about what happens if you have it and want a family.

So was wondering if anyone knows how it's actually passed on to children or what the actual chances are of them having it etc. He wants to have children, but his concerns put him off, so I'm trying to reassure him.

Sorry if that's a bit confused/confusing.

Thanks very much in advance!

Lulabell

Thanks for that, I hadn't seen it before. Don't know how my search engine missed it seem's to be a fairly obvious one lol.

Hard to get a referral as my partner is American and all his details are registered over there. He'd have to be fully reassessed to prove he has it etc. At the mo we're still trying to get him on the blind register for the UK, but first appointment for an opthamologist is in August (to be fair, he's been here for a few years and has been lazy about getting it done). Basically it'd take ages and we're not 100% which country we'll be in in a few months time, so for now I'm just trying to cobble some stuff together until we're sorted. I think when the time comes they can do a test to check I'm not a carrier, but for now I'm just trying to talk him round to the idea with a few choice figures

Hello Lulabell. I'm awfully sorry but I'm not really going to be able to help because there are several different forms. It can be X linked, as fio says, but it can be autosomal recessive, and the chances of passing it on are going to differ wildly depending on what type it is. I can try my best with both possible scenarios if you like, but either way the chances of passing it on are not that great (unless there's a dominant form I haven't come across).

Fio, yes of course, any time

Hi Tamum,

There's zero history of it in my family, which I know doesnt mean anything for sure, but we're assuming that I'm not a carrier (will get it checked though when we're a bit further along). I dont know if it helps at all but on his father's side there are loads of boys but no OA, and on his mother's side he's the only one (no uncles etc) and he has it. I know that's completely unscientific, sorry!

Essentially, I think his concern is whether he could pass it on, so does the mother have to be a carrier as well in that case? Also, I know it mainly affects boys, but would his daughters be likely to be carriers?

Sorry, don't know if that's any more workable. If not, I can at least say that the chances aren't as high as he seems to think.

Personally I would take the risk anyway, it seems slight and he copes fine with it, despite having a pretty severe form, and is about to finish his PhD so it's hardly slowed him down!

Thanks so much

I;ve just had a look at OMIM, and I can't see any sign of a dominant form; so with that and assuming your partner doesn't have a parent with the same thing, I will assume it's either the X linked or recessive form. If it's X linked, your daughters will have a 50:50 chance of being carriers, but are unlikely to be affected (there is always a faint possibility of a very mild form of X linked disorders manifesting in daughters because of something called non-random X inactivation).

If it's recessive then the issue is whether you are a carrier. As far as I can make out, autosomal forms of ocular (as opposed to oculocutaneous) albinism are very rare, so the chances of you being a carrier are similarly rare. If it is this form, and you are not a carrier, then your children all have a 50:50 risk of being carriers, but no chance of being affected.

All in all it seems likely that things are not too bleak, but I would strongly advise you to get genetic counselling- I am an academic geneticist but not a medic, so there may be something I've missed. Good luck

Hi Lulabell,

I'm a molecular biologist who knows a bit about genetics - will that do?! I've looked at the site that Fiofio posted and it seems to explain it pretty clearly, but if there's anything you don't understand I might be able to help. Unfortunately I think it will be impossible to work out your chances of having a child affected without knowing what type of ocular albinism he has, as according to this link different forms are carried in different ways which have different patterns of inheritance. If you're not a carrier though, it looks like the chances of yoru child being affected are very low. Good luck!

Oops sorry x post with Tamum - sure she will be much more help!

Thanks so much for that that's much better than I was hoping. I'm assuming they can do a test to find out which kind he has etc, so I'll let him know and hopefully he'll be more optimistic about it.

Thanks for your help and advice.

Lulabell

Oh sorry, cross posted- no, that's not unscientific at all, it sounds completely compatible with X linked inheritance (note that I am being careful with my wording though!). OK, so bear in mind that females are XX and males are XY... your sons will not be at risk at all if it is X linked- your partner will only pass his Y chromosome on to them. Your daughters (I am kindly granting you a huge family here ) will all onherit his X chromosome so will be obligate carriers, but should be protected from manifesting it by their other X chromosome from you. The fact that they are likely to be carriers is also a good reason for going for genetic counselling, as they might want to store bloods and so on so they could offer your daughters screening later on, if that's what they wanted.

Oh no fearscape welcome on board Lulabell, I am not sure whether they have identified the genes involved in all forms but I bet they will be able to help. You need Bluebear for testing stuff but she has a new name and I can't for the life of me remember what it is

Sorry fearscape, I x posted with you

Thanks for that, I'm going to read that site in more depth and see if they have further links etc.

Actually, I'm a bit confused by 'autosomal' , is there a less technical term?

Thanks

Lol, super x posting going on. Thank you so much for all your help!

Thank you for my huge family would daughters all definitely be carriers, or is that just a 50/50 chance say?

I have to admit, I'm working on the theory that medicine will advance by the time my daughters want children, and it should be easier to solve, not sure how that will pan out though...

Hello again If it is X linked, then all your daughters will definitely be carriers, no escape I'm afraid. As you say, there may well be huge advances by that time though. Autosomal means not on the sex chromosomes basically- for an autsomal recessive disease both parents need to be carriers, or to have the disease themselves (I am bandying the term "disease" about here, sorry). In your case, if it is autosomal (seems unlikely, but just in case) your partner would have 2 copies of the OCA gene and you would have none (most likely) or one (we know you can't have two because you haven't got the condition). That means that your children would have one copy from your partner and would definitely be carriers. If you are a carrier then half of them would be affected and half would be carriers.

This is driving me mad- I could explain it so much better with a pen and paper!

Lol, sorry to have plagued you, that all makes much more sense now though thank you. I'll leave you alone now, I promise

I imagine that there's probably a handy diagram the pen and paper way lol

Thank you again

Oh no, you haven't plagued at all, just ask away. CAT me if that would help, if you have any more questions. At least that way I could draw a picture and scan it in