This document summarizes abnormalities in carbohydrate metabolism, including deficiencies in disaccharides like lactose and sucrose. It discusses clinical diagnosis, causes, and diseases associated with deficiencies in galactose, fructose, and pentose metabolism. Key points covered include lactose intolerance caused by lactase deficiency; sucrase-isomaltase deficiency diagnosed using breath tests; hereditary fructose intolerance from aldolase B absence; and galactosemia from galactose-1-phosphate uridyl transferase deficiency. Disorders of glucose metabolism like diabetes and hypoglycemia are also briefly mentioned.

1. CLINICAL BIOCHEMISTRY 1
Lecture No 4+5
Abnormalities of carbohydrates
metabolism
by Prof. Mohamed Afifi

2. Disaccharides Deficiencies
Clinical diagnosis
Cause
Disease
1- inability for digestion of lactose
with fermentation by intestinal
bacteria.
2-Lactose Intolerance
Test (Hydrogen Breath Test,
Lactose Breath Test , Disaccharide
Absorption
(
Test, Oral Lactose
Tolerance
In breath test the increase of
hydrogen gas is indicator. In blood
test if glucose not increased with
symptoms abdominal symptoms is
indicator
Lactase
deficiency
Lactase deficiency
(hypolactasia or
lactase
nonpersistence, lac
tose intolerance )

3. Disaccharides Deficiencies
Clinical diagnosis
Cause
Disease
1-intestinal wall cells sucrase-isomaltase
activity in the tissue samples was low in
comparison to the level of enzyme activity
found in a normal population
2- BREATH TESTS
A- The carbon-13 breath test
B-hydrogen-methane breath test
3- 4-4-4 ORAL SUCROSE CHALLENGE TEST
Sucrase–
Isomaltase
Deficiency
Sucrase–
Isomaltase
Deficiency)
A fasting patient simply drinks a well-dissolved solution of 4 tablespoons of table sugar in a 4-
ounce glass of water. If sucrase-isomaltase activity is diminished or absent, within 4 hours the
patient will experience the GI symptoms associated with CSID, such as gas, bloating, abdominal
distention (swelling), or diarrhea. This test is not appropriate for infants, young children,
geriatric patients, and those with co-morbid conditions like diabetes. Patients may have severe
symptoms if they are very sensitive to sugar. A physician should be consulted before this test is
taken

4. Glycogen storage disease

5. Fructose metabolism

6. Abnormalities of fructose metabolism
Clinical diagnosis
Cause
Disease
1 increase of fructose in blood
2- Fructose in urine
3- decrease of hepatic
fructokinase
Lack of hepatic
fructokinase
Essential
fructosuria
1- absence or decrease of hepatic aldolase B
2- Increase of blood sorbitol
3- fructose in urine
4- generalized aminoaciduria
5- fructose tolerance test
6-hypoglycemia
7- increase uric acid and decrease inorganic
phosphate.
Absence of
hepatic
aldolase B
Hereditary
fructose
intolerance
(HFI)
Fructose-1,6-
bisphosphatas
e deficiency
Fructose-
induced
hypoglycemi
a

7. Galactose metabolism

8. Abnormalities of galactose metabolism
Clinical diagnosis
Cause
Disease
1 increase of galactose in blood
2- galactose in urine
3-Galactitol and galactonic acid in
blood and urine
4- deficiency of glactokinase I RBCs
Galactokinase
deficiency
Galactokinase
defeciency
1 increase of galactose in blood
2- galactose in urine
3-Galactitol and galactonic acid in
blood and urine
4- deficiency of Glactose-1-
phosphate uridyl transferase RBCs
5- Generalized aminoaciduria and
proteinuria
.
Glactose-1-
phosphate
uridyl
transferase
deficiency
Galactosemia

9. 1- red cell galactose-1-
phosphate is increased
2- GALT is normal
3-Epimerase in
erythrocytes is low or
absent
4- GALE gene
sequencing
Uridine
diphosphate-
galactose 4′-
Epimerase
deficiency
Uridine
diphosphat
e-galactose
4′-
Epimerase
deficiency
(GALE )

10. DISORDERS OF PENTOSE METABOLISM
Clinical diagnosis
Cause
Disease
Decrease the activity of RBCs G6PDH
Glucose 6
phosphate
deficiency
Favism
1- decrease of transaldolase
Activity in fibroblasts, lymphoblasts, or
liver tissue.
2-Elevated urine erythritol, arabitol, ribitol,
sedoheptitol, perseitol, sedoheptulose,
mannoheptulose, and sedoheptulose-7P
3- Sequencing of transaldolase gene. .
Transaldolase
Deficiency
Transaldolase
Deficiency
fibroblast homogenates showed deficient
activity in ribose-5-phosphate isomerase.
Ribose-5-
Phosphate
Isomerase
Deficiency
Ribose-5-
Phosphate
Isomerase
Deficiency
The urine contains l-xylulose, which is
excreted in increased amounts (1–4 g daily
xylitol
dehydrogenase
deficiency
Essential
Pentosuria

11. Abnormalities of glucose metabolism
1- Hyperglycemia
2- DM
3-hypoglycemia
4- Glucosuria
In text book from page 56-64