Genetics still a jumble

I'd love to report that our second visit with the geneticist and genetic counselor cleared up the genetic muddle we were in. The truth is we are only slightly less confused than before about what role genetics probably plays in C.'s disabilities.

The geneticists were certainly not to blame. They were generous with their time (50 minutes - which resembles one of those alternative "practitioner's" sessions). They made an admirable effort to  dumb-down the material for our lay minds to the point where we almost got a-lot-of-it.

Here's my take of what they tried to tell us based on memory, my notes and their written summary.

1. We learned that contrary to what they had told us in the past, the fact that C. was born impaired after several healthy siblings does not mitigate the chance that her disabilities are hereditary. If the hubby and I are carriers of something genetic, there's still that 50/50 chance with every birth.
2. We learned that the cost of further Rett Syndrome testing is nearly as expensive as the broader tests.
3. We learned that there really isn't a strong basis for suspecting that C. has Rett Syndrome. This emerged  only after I pressed the doctor for specifics about that. It seems that she had been relying on the fact that a previous neurologist had sent us to this country's top Rett expert. But we pointed out that that young neurologist had never really assessed her. (He was cutting his teeth on C. because the senior doctors in the clinic had lost interest and fobbed her off onto him). His reports were always direct transcripts of our reports to him. Anyway, even the Rett expert whom we saw wrote that the chance C. has Rett is "not a strong one". I also pointed out to the geneticist that the course of C.'s impairments does not jive with that of Rett,something she wasn't aware of.
   Rett timeline: normal development in the first few months of infancy, followed by gradual deterioration.
   C.'s timeline: abnormal development from birth until sudden dramatic deterioration following the eruption of her epilepsy and weeks of status epilepticus.
   The geneticist did a 180 at that point and advised us to delete further Rett testing from our list of options.
4. We learned that the results of our most recent genetic test, the CMA, disclosed that C. has a Duplication on Chromosome 17 and a Deletion on Chromosome 2. The hubby has neither of these. But I was found to have the same duplication on Chromosome 17, though not the deletion. This means that if the Deletion is the cause for C.'s disabilities, then it is a de novo mutation (not inherited, a one-off event). In that case, our other children would not need to worry about it being repeated in their offspring. Of course, we're still stuck with that persistent "if".
5. The possibility still exists that this is not de novo but that C. inherited some genetic abnormality that these few tests we've done haven't discovered. But even then, the risk of our other children passing it on is "very low", to quote the geneticist. One situation in which it would be feasible is if it is "X-linked" and if C. has "Skewed X inactivation". This would mean that our other daughters might also be carriers of the abnormality. If so, they are asymptomatic because they don't have the skewing but could pass it on to male offspring.  There's an affordable blood test for skewing that can be done on C. to check out this hypothesis

I'm afraid that's as much detail as I can handle. Any questions about the above summary would stump me. There's a good reason I avoided the sciences at college like the plague. My science-aptitude genes are undoubtedly "skewed". No need for a blood test to confirm that.

Conclusion: the best course would be to get the full exome testing. This expensive test (about US $6,800 at today's prices to test C., the hubby and me) will only be an option if our insurance covers it. We're in the process of inquiring about that. If we find that it isn't covered, we'll settle for that "skewing" test.