Biochemistry: Diseases

Question 1

Fructose in urine and blood, otherwise asymptomatic

Answer 1

Essential fructosuria

Question 2

What enzyme is deficient in essential fructosuria?

Answer 2

Fructokinase

Question 3

Hypoglycemia, jaundice, cirrhosis, and vomiting following consumption of fruit, juice or honey with reducing sugar in the urine

Answer 3

Fructose intolerance

Question 4

What enzyme is deficient in fructose intolerance?

Answer 4

Aldolase B

Question 5

How do you treat fructose intolerance?

Answer 5

Decrease intake of fructose and sucrose (glucose+fructose)

Question 6

What is the pathophysiology of fructose intolerance?

Answer 6

Fructose -1P builds up, decreasing available phosphate so glycogenolysis and gluconeogenesis cannot occur

Question 7

Galactose in blood and urine, infantile cataracts

Answer 7

Galactokinase deficiency, very mild

Question 8

Failure to thrive, jaundice, hepatomegaly, infantile cataracts, MR

Answer 8

Classic galactosemia

Question 9

What enzyme is deficient in classic galactosemia?

Answer 9

Uridyltransferase

Question 10

What is the role of aldose reductase?

Answer 10

Provides an alternate means of trapping glucose in the cell, converts it to sorbitol which can then be converted to fructose

Question 11

What are the essential amino acids?

Answer 11

Phenylalanine, Valine, Tryptophan, Threonine, Isoleucine, Methionine, Histidine, Leucine, Lysine

Question 12

Hyperammonemia, increased ornithine

Answer 12

N-acetylglutamate deficiency (necessary cofactor of CMP-1 in urea cycle)

Question 13

Increased orotic acid in blood and urine, low BUN and symptoms of hyperammonemia in the first few days of life

Answer 13

Ornithine transcarbamylase deficiency (Urea cycle, most common)

Question 14

How is ornithine transcarbamylase deficiency inherited?

Answer 14

XLR

Question 15

MR, growth retardation, seizures, fair skin, eczema, musty body oder

Answer 15

Phenylketonuria

Question 16

What enzyme is deficient in PKU?

Answer 16

Phenylalanine hydroxylase

Question 17

How is PKU transmitted, how is it detected and how is it treated?

Answer 17

1. AR
2. Screening 2-3 days after birth
3. Decrease phenylalanine, increased tyrosine and avoid artificial sweetner

Question 18

Dark connective tissue, dark brown sclerae, urine turns black on prolonged exposure to air

Answer 18

Alkaptonuria, cannot degrade tyrosine

Question 19

What enzyme is deficient in alkaptonuria?

Answer 19

Homogentisate oxidase

Question 20

High levels of homocystine in the urine, MR, osteoporosis, tall stature, kyphosis, lens subluxation

Answer 20

Homocystinuria

Question 21

What enzyme is deficient in homocystinuria?

Answer 21

1. Cystathionine synthase, OR
2. B6, OR
3. Homocysteine methyltransferase

Question 22

Renal stones at a young age

Answer 22

Cystinuria

Question 23

What enzyme is deficient in cystinuria?

Answer 23

Renal PCT and intestinal amino acid transporter of Cystine, Ornithine, Lysine and Arginine

Question 24

How do you treat cystinuria?

Answer 24

Alkalinize the urine

Question 25

CNS defects, MR, urine that smells like burnt sugar, death

Answer 25

Maple Syrup Urine Disease

Question 26

What enzyme is deficient in maple syrup urine disease?

Answer 26

Decreased amounts of alpha-ketoacid dehydrogenase (can’t break down branched amino acids, ILV)