Question

A healthy couple, who recency emigrated from Eastern Europe. bring their 3-year-old son to the office for evaluation of an eczematous rash. On examination, the child also shows signs of intellectual disability and gait abnormality and has a musty body odor. What is the likelihood that this couple's next child will be affected with the same disease?

A. Same as the general population
B. 1/32
C. 1/16
D. 1/8
E. 1/4
F. 1/2

Answer 1

The likelihood that the couple's next child will be affected with the same disease, which appears to be Phenylketonuria (PKU), is 25% or 1/4.

Step-by-step explanation:

The child's symptoms suggest a diagnosis of Phenylketonuria (PKU), which is an autosomal recessive disorder. Both parents must be carriers of the defective gene that causes PKU for the child to be affected. If both parents carry one copy of the mutated gene and one normal gene, they are carriers but typically do not show symptoms of the disease. When two carriers have a child, there is a 25% chance (1 in 4) that the child will inherit two copies of the mutated gene, one from each parent, and thus be affected by the disease. There is also a 50% chance the child will be a carrier (inheriting one normal gene and one mutated gene), and a 25% chance the child will inherit two normal genes.