We are glad that your son is seeing a medical geneticist and encourage you to continue to do so. We do not quite understand the information your provided about your son's chromosome abnormality (5p or 5q?, is there a chromosome deletion?, etc) and whether or not he has a diagnosis of spinal muscular atrophy (SMA).
To give you some information on SMA, the primary cause of SMA is believed to be mutations in a gene called SMN1 at the location 5q13.
Both parents of an affected person are usually carriers (have only one mutation). Two carriers have a 25% chance with each pregnancy to have an affected child, but typically do not have symptoms themselves. Of note, approximately 2% of people affected with SMA have one de novo mutation in the SMN1 gene, meaning that one mutation occurs sporadically, while the other is inherited from a carrier parent.
About 95% of individuals affected with SMA have a deletion in a portion of the SMN1 gene called exon 7 in both copies of the gene. These individuals are said to be homozygous for this deletion. In about 5% of people affected with SMA, only one copy of the SMN1 gene is missing exon 7, and the other copy of the gene has a different type of mutation in the gene. Thus far, researchers have identified nearly 30 such disease-causing mutations.
Extra copies of a gene called SMN2 appear to modify the severity and age of symptom onset of SMA. The SMN2 gene is located adjacent to the SMN1 gene on chromosome 5 at the location q13.
We hope this information is helpful and wish you and your son the best of luck!
Thank you for your response. My son's chromosone is 5q31 - 5q33.1. This information is very helpful. Do you think it would be alright if I gave this information to my geneticist?
Thank you very much for this information.