Still Waiting

Still waiting on the latest round of lab results concerning the "imprinting defect" genetic mechanism they are testing on Kendal. The following are some notes I found on the Angelman Syndrome Foundation website regarding this possible mechanism that Kendal may have...

A fourth class of AS individuals (3-5% of cases) have inherited chromosome 15 copies from both mother and father, but the copy inherited from the mother functions in the same way that a paternal chromosome 15 should function. This is referred to as an “imprinting defect”. A small percentage of AS individuals with imprinting defects have very small DNA deletions in a region called the Imprinting Center (IC) 14-17 but all AS individuals with IC defects have abnormal DNA methylation changes in this region. The IC is located some distance from the UBE3A gene but it is still able to regulate UBE3A by a complex mechanism that is the subject of intense research. In some cases, AS caused by imprinting defects can recur in more than one member of a family. It has recently been discovered that assisted reproductive technologies (ART), such as in vitro fertilization (IVF) or intra-cytoplasmic sperm injection (ICSI), are associated with a few cases of AS due to the non-deletion type of IC defect.

Individuals with AS due to IC defect can have either inherited this mutation from a normal mother or have received the mutation spontaneously (i.e., not inherited). In the former case, the theoretical recurrence risk is 50% and in the latter (i.e., spontaneous mutation) the risk is believed to be less than 1%.