While managing the care of your 18-year-old patient with a thoracic aneurysm with dissection (TAAD), your patient reveals to you that his grandfather suffered from the same condition but was not diagnosed until the age of 63 when he first developed symptoms. What is the phenomenon in which one individual in a family may present with symptoms at a young age, whereas another individual may present at an elderly age?

Question

Quizplus · Accepted Answer

Variable expressivity is defined as a variation in disease symptoms among persons with the same mutation. In this case the variation refers to the age of onset of the symptoms, thus D is the correct answer. Penetrance refers to the proportion of individuals carrying a particular mutation who also express an associated, observable trait. Genocopy refers to a genotype that determines a phenotype which closely resembles the phenotype determined by a different genotype. Genetic heterogeneity represents the production of the same or similar phenotypes by different genetic mechanisms; the character of a phenotype produced by mutation at more than one gene or by more than one genetic mechanism.

While Managing the Care of Your 18-Year-Old Patient with a Thoracic