MENDELIAN DISORDERS
A 23-year-old black primigravida is seen at 12 weeks' gestation. She has
been diagnosed with sickle cell trait (AS). Her husband and father of the
baby is also AS. She inquires as to the risk of her baby having sickle cell
disease (SS).About 1% of liveborn infants have a congenital Mendelian disorder. About 15%
of all birth defects are attributable to Mendelian disorders; of these, 70% are
autosomal dominant. The remainder are autosomal recessive or X-linked.
Autosomal dominant
Transmission occurs equally to males and females, and serial generations are
affected. Gross anatomic abnormalities are the most common findings. Age
of onset is usually delayed, with variability in clinical expression.