Parental somatic mosaicism is underrecognized and influences recurrence risk of genomic disorders.

New human mutations are thought to originate in germ cells, thus making a recurrence of the same mutation in a sibling exceedingly rare. However, increasing sensitivity of genomic technologies has anecdotally revealed mosaicism for mutations in somatic tissues of apparently healthy parents. Such somatically mosaic parents might also have germline mosaicism that can potentially cause unexpected intergenerational recurrences.

A general approach to genetic counseling.

Genetic counseling can best be performed if a systematic approach is taken. The geneticist or genetic counselor has the difficult task of conveying complex information to patients in an understandable form. At the same time, this must be done in a nondirective manner, affording the patient the right to make his or her own decisions.