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Confused: Shouldn't a blood test and a full array show DMD?

Andrew (6 1/2) has not presented in a typical way of DMD. He didn't start walking till after his 3rd Birthday and he has been extremely delayed in many other ways. The doctors have also agreed he is not a typical DMD boy and have tested him for other things. He has had two arrays done. Both we were told would find his deletion (exon 70) of the DMD gene and also could find other things. The arrays both came back normal? No Dmd deletions? How is this possible if he's been diagnosed through a muscle biopsy to have DMD? Looking for answers. Thanks.

Alissa

PS. The gentics conselor we say is out of town till next week so I have to wait till next week to get a better answer from her.

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Permalink Reply by carrie on December 29, 2011 at 4:37pm

This presentation (developmental delay) is not so unique for those with deletions after exon 63. If the the muscle biopsy demonstrates no dystrophin protein expression staining, this can lead to DMD diagnosis. It is possible that some DNA mutations would stil not be detected using the arrays---ie some intronic mutations. Other sequencing methods could be used. I can refer you to someone well versed in this once you get the test results back and are looking for additinal strategies to find mutations. Why do you think that the exon 70 deletion is the likely culprit?

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Permalink Reply by Ofir Arad on December 29, 2011 at 10:55pm

As Carrie says mutations after exon 63 can explain the developmental delay. A mutation after exon 63 causes the lack of expression of all the isoforms of dystrophyn including dp71 that is important for the the brain development. You can find a better explanation in the attached paper. My son has a mutation in exon 61 but he also has a lot of behavioral problems. Today we took him to a psychiatrist and he said that he may have an autistic spectrum disorder. So I think that maybe is more effective to try to treat the symptoms than to try to find the genetic causes. In any case I hope you to find a quick and clear diagnose because I know that this situation is exasperating.

Attachments:

Hum. Mol. Genet.-2009-Daoud-hmg-ddp320.pdf, 718 KB

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Permalink Reply by Susan Rathfelder on January 1, 2012 at 2:26pm

Alissa,

My son Jonathan's diagnosis was confirmed by a muscle biopsy. He has had the muscle biopsy tests at two different labs and 4 blood DNA tests and they have not been able to identify his particular mutation. I believe I have heard that there are about 5% of boys that at this point they may not be able to identify mutations, but technology is advancing so hopefully they will be able to in the near future. Jonathan recently gave a skin biopsy sample and some blood while at UCLA for research into identifying difficult mutations. Carrie's husband is doing some of this research.

Susan