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CASE FILES: BIOCHEMISTRY
C O M P R E H E N SIO N Q U E ST IO N S
[24.1] A 22-year-old soldier collapses from dehydration during maneuvers in
the desert and is sent to a military hospital. Prior to enlisting, a physi-
cian observed a high level of glucose in his urine during an examina-
tion. At first, he was not allowed to enlist because he was suspected of
being a diabetic. Further tests, however, determined that his insulin
level was normal. A glucose tolerance test exhibited a normal pattern.
Laboratory tests following his dehydration episode repeat the previous
findings, but further testing of the urine reveals that only
D
-glucose is
elevated. Other sugars were not elevated.
This patient’s elevated urinary glucose and his dehydration episode are
caused by a deficiency in which of the following?
A. GLUT 2
B. GLUT 4
C. Insulin receptor
D. SGLT1
E. SGLT2
[24.2] Your patient is a 7-month-old baby girl, the second child born to unre-
lated parents. She did not respond well to breast-feeding and was
changed entirely to a formula based on cow’s milk at 4 weeks.
Between 7 and 12 weeks of age, she was admitted to the hospital twice
with a history of screaming after feeding, but was discharged after
observation without a specific diagnosis. Elimination of cow’s milk
from her diet did not relieve her symptoms; her mother reported that
the screaming bouts were worse after the child drank juice and that she
frequently had gas and a distended abdomen. Analysis of a liver nee-
dle biopsy did not reveal any liver enzyme deficiencies. Overall, the
girl is thriving (weight greater than 97th percentile) with no abnormal
findings on physical examination.
If a biopsy of intestinal tissue were obtained from your patient and ana-
lyzed, which of the following would most likely be deficient or
defective?
A. GLUT 2
B. GLUT 5
C. Isomaltase
D. Lactase
E. SGLT1
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