USMLE® Step 1 style questions USMLE
A 6-year-old girl is brought to the clinic by her parent due to repeated episodes of jaundice, pallor, and fatigue for the last 8 months and new-onset abdominal pain for the last 3 days. She is at the 35th percentile for height and 20th percentile for weight. The parent reports no pregnancy or birth-related complications and states that the patient had been relatively healthy previously. The parent states that the girl’s biological father had been hospitalized with similar symptoms as a child and had abdominal surgery, but the details of the surgery are unknown. The patient’s temperature is 37°C (98.9°F), pulse is 90/min, respirations are 24/min, and blood pressure is 118/72 mmHg. Physical examination shows an ill-appearing pale child with scleral icterus and splenomegaly. Laboratory tests are obtained and the results are shown below.
The patient most likely has a defect in which of the following?
Hereditary spherocytosis (HS) is an autosomal dominant genetic disorder in which red blood cells are sphere-shaped instead of having the normal biconcave shape. These abnormal red blood cells break down prematurely, which can lead to anemia. Also, because of their abnormal shape, red blood cells in spherocytosis don't move through small blood cells efficiently as normal ones do, which can affect tissue oxygenation. People with hereditary spherocytosis can present with jaundice, splenomegaly, and features of anemia like pallor and fatigue.