A 25-year-old Mediterranean female presents to her obstetrician at 12-weeks
gestation for her first prenatal visit. This is her first pregnancy, and she is con-
cerned about her baby and the risk of inheriting a “blood” disease like others
in her family. The patient reports a personal history of mild anemia but noth-
ing as severe as her brother who required frequent transfusions and died at
age 10. The patient was told by her physician that she did not need to take iron
supplementation for her anemia. Patient denies having any anemic symptoms.
Her physical exam is consistent with a 12-week pregnancy and ultrasound
confirmed an intrauterine pregnancy at 12-weeks gestation. The patient’s hemo-
globin level shows a hypochromic, microcytic (small sized red cell) anemia
(hemoglobin, 9g/dL) and hemoglobin electrophoresis demonstrated increased
hemoglobin A2 level (4.0 percent) and increased fetal hemoglobin level, a
pattern consistent with P-thalassemia minor. The patient underwent chorionic
villus sampling to assess whether the fetus was affected, and the diagnosis
returned in several hours.
What is the molecular genetics behind this disorder?
What was the likely test and what is the biochemical basis?