A 24-year-old woman comes to the office at 12 weeks gestation for prenatal counseling. She is 120 cm (3 ft 11 in) tall with short upper and lower extremities but normal torso length. Her husband is phenotypically normal and has no medical problems. The patient knows that there is a 50% chance of passing on her condition to the fetus. An abnormality involving which of the following cells is most likely responsible for this patient's features?

Question

A 24-year-old woman comes to the office at 12 weeks gestation for prenatal counseling.  She is 120 cm (3 ft 11 in) tall with short upper and lower extremities but normal torso length.  Her husband is phenotypically normal and has no medical problems.  The patient knows that there is a 50% chance of passing on her condition to the fetus.  An abnormality involving which of the following cells is most likely responsible for this patient's features?

Quizplus · Accepted Answer

Eductional Objective: Unlike the process of intramembranous ossification that forms flat bones, endochondral ossification proceeds along a cartilage template and is responsible for the formation of long bones.  Achondroplasia is characterized by an exaggerated inhibition of chondrocyte proliferation in the growth plates of long bones and manifests with proximal limb shortening, midface hypoplasia, and macrocephaly.

A 24-Year-Old Woman Comes to the Office at 12 Weeks