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Enzyme Deficiencies Flashcards

1
Q

What is the causative enzyme for PKU (phenylketonuria)?

A

phenylalanine hydroxylase (PAH)

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2
Q

Which metabolic pathway does Phenylalanine hydroxylase act in?

A

Amino Acid metabolism

- responsible for converting phenylalanine to tyrosine

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3
Q

What is an inborn error of metabolism?

A

general term for diseases caused by mutations to genes involved with metabolic pathways

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4
Q

What precursor builds up in PKU?

A

phenylalanine which then turns to phenylpyruvic acid

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5
Q

How do you treat PKU?

A

keep on a strict diet low in phenylalanine

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6
Q

What enzyme is deficient in Oculocutaneous Albinism?

A

tyrosinase - necessary for formation of melanin

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7
Q

Because of the deficiency of tyrosine in PKU pateints, how to they tend look?

A

blond hair

blue eyes due to deficiency of melanin

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8
Q

Lack of pigment in Oculocutaneous Albinism, leads to what clinical symptoms?

A
  • poor visual acuity
  • nystagmus (pendular eye movement)
  • underdeveloped fovea
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9
Q

What enzyme is deficient in Maple Syrup Urine Disease?

A

branched-chain ketoacid decarboxylase

Maple trees have branches.

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10
Q

What is the result of Maple Syrup Urine Disease?

A

Valine (val), leucine (leu) and isoleucine (ile) are excreted in the urine

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11
Q

What symptoms are present in the first week if newborns have Maple Syrup Urine Disease?

A

vomiting, alternating tone

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12
Q

What is the treatment for Maple Syrup Urine Disease?

A

dietary restriction of val, leu and ile

still susceptible to deterioration

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13
Q

What is the most common carbohydrate metabolism disorder?

A

Glucose-6-phosphate dehydrogenase deficiency

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14
Q

The glucose-6-phosphate dehydrogenase is responsible for what? pathway?

A

oxidative steps of the pentose phosphate pathway

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15
Q

What inheritance pattern is Glucose-6-phosphate dehydrogenase deficiency?

A

x-linked recessive

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16
Q

Glucose-6-phosphate dehydrogenase deficiency leads to reduced ability to produce _________?

A

NADPH (potent reducer used by cells to protect against oxidative damage)
-pentose phosphate pathway

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17
Q

Which cell type is most affected by Glucose-6-phosphate dehydrogenase deficiency? Why?

A

RBC no nucleus to provide other reducing sources
susceptible to oxidative damage

-results in anemias

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18
Q

What populations are more likely to be affected by Glucose-6-phosphate dehydrogenase deficiency?

A

African
Asian
Middle Eastern
Mediterranean

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19
Q

What are the three main sources for oxidative assaults that would cause symptoms of Glucose-6-phosphate dehydrogenase deficiency?

A

INFECTION - cold, flu, sinus infections
DRUGS - NSAIDs, quinolones, sulfa drugs, Tylenol, naphthalene, artificial food coloring
FOOD - fava beans and other legumes, sulfites, menthol-containing foods (toothpaste, mouthwash)

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20
Q

Acute oxidative damage from Glucose-6-phosphate dehydrogenase deficiency can lead to hemolytic anemia which presents with?

A 
paleness
jaundice
dark urine
fatigue
shortness of breath/rapid heart rate
splenomegaly
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21
Q

What treatments are available for Glucose-6-phosphate dehydrogenase deficiency?

A

dietary restriction

drug restriction

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22
Q

Galactosemia is due to a deficiency is what enzyme?

A

galactose-1-phosphate uridyl transferase

involved with breakdown of dietary sugar galactose

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23
Q

What are the symptoms of galactosemia?

A

newborns present with vomiting, lethargy, failure to thrive, and jaundice within 2 weeks

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24
Q

If untreated, galactosemia can lead to what?

A

mental retardation
cataracts
liver cirrhosis

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25
What treatments are available for galactosemia?
feed formulas lacking in milk sugars (galactose and lactose)
26
Hereditary Fructose Intolerance results from deficiency in what enzyme?
fructose-1-phosphate aldolase (involved in breakdown of dietary fructose)
27
When does Hereditary Fructose Intolerance present and what are the symptoms?
presentation age varies (depends on when foods with fructose are introduced) Symptoms: minimal to severe Severe: failure to thrive, vomiting, jaundice and seizures
28
How would you treat Hereditary Fructose Intolerance?
fructose food restriction
29
List the 4 glycogen storage diseases affecting the liver.
``` Von Gierke (breakdown) Cori (breakdown) Anderson (synthesis) Hepatic phosphorylase deficiency (breakdown) ```
30
Which enzyme is deficient in Von Gierke?
glucose-6-phosphate
31
Which enzyme is deficient in Cori disease?
amylo-1,6-glucosidase (debrancher enzyme)
32
Which enzyme is deficient in Anderson disease?
glycogen brancher enzyme (synthesis of glycogen) | 4,6 transferase
33
What is the inheritance pattern for hepatic phosphorylase deficiency?
autosomal | x-linked
34
How does Von Gierke present?
hepatomegaly hypoglycemia infants-sweating, fast HR
35
How does Cori disease present?
hepatomegaly | muscle weakness
36
How does Anderson present?
hypotonia | abnormal liver function w/i first year >>>liver failure
37
How does hepatic phosphorylase deficiency present?
hepatomegaly hypoglycemia failure to thrive
38
How would you treat Von Gierke disease?
frequent feeding to reduce hypoglycemia | avoid fasting
39
How would you treat Cori disease?
frequent feeding to reduce hypoglycemia
40
How would you treat hepatic phosphorylase deficiency?
carbohydrate supplementation
41
List 2 glycogen storage diseases affecting muscle.
Pompe | McArdle
42
Which enzyme is deficient in Pompe?
a-1,4-glucosidase (necessary for glycogen breakdown)
43
Which enzyme is deficient for McArdle?
muscle phosphorylase (necessary for breakdown of muscle glycogen during exercise)
44
How does Pompe present?
in infancy with hypotonia, delay in gross motor milestones enlarged heart cardiac failure within 2 years
45
What treatment is available for Pompe?
no current treatment | -experimenting with enzyme replacement therapies
46
How does McArdle present?
presents in ADOLESCENSE with muscle cramps during exercise
47
What treatment is available for McArdle?
no current treatment
48
List 2 steroid metabolism disorders.
Congenital Adrenal Hyperplasia (CAH) | Androgen Insensitivity Syndrome
49
What is the most common cause of ambiguous genitalia in female newborns?
Congenital Adrenal Hyperplasia (CAH)
50
In 90% of cases Congenital Adrenal Hyperplasia (CAH) is due to what enzyme deficiency?
21-Hydroxylase
51
25% of Congenital Adrenal Hyperplasia (CAH) cases have the salt-losing form. How does it present?
2-3 weeks of life with circulatory collapse - hypernatremia - hyperkalemia
52
What is the inheritance pattern of Congenital Adrenal Hyperplasia (CAH)?
autosomal - seen in males - ambiguous genitalia in females
53
Affected females are virilized due to accumulation of ?
adrenocorticosteroids (many have testosterone-like functions)
54
How are Congenital Adrenal Hyperplasia (CAH) infants treated?
replacement cortisol for life (with increases given during times of stress) **fludrocortisone is given as well in salt-losing forms *plastic surgery for females
55
Androgen insensitivity syndrome is due to defect in what?
defective testosterone receptor | normal levels of testosterone are produced but due to lack of receptors genes cannot be expressed
56
When is Androgen insensitivity syndrome identified?
not identified until lack of menses in cases of "inguinal" hernia which is actually internalized testes
57
What is the inheritance pattern of Androgen insensitivity syndrome ?
x-linked recessive | 46 XY
58
List a lipid metabolism disorder.
Familial Hypercholesterolemia
59
What is the inheritance pattern for Familial Hypercholesterolemia?
autosomal dominant single-gene | **associated with high morbidity and mortality
60
How can Familial Hypercholesterolemia present in childhood?
xanthomata - buildup of cholesterol under the skin
61
How would you treat Familial Hypercholesterolemia?
``` dietary restriction statin drugs (HMG-CoA reductase inhibitors) ```
62
What is the result of the mutation in Familial Hypercholesterolemia?
problems with the LDL receptor
63
What are the 4 main classes of problems with the receptor?
1. Reduced/defective biosynthesis 2. Reduced/defective transport 3. Abnormal binding of LDL by the receptor 4. Abnormal internalization of the receptor
64
What are the two lysosomal storage disorders?
Mucopolysaccharidosis | Sphingolipidosis
65
What is the most common Mucopolysaccharidosis?
Sanfilippo syndrome
66
How does Sanfilippo Syndrome (Mucopolysaccharidosis) present?
2nd year of life - coarsening of features, skeletal changed, progressive intellectual loss, seizures and death in early adult life
67
What enzyme is deficient in Mucopolysaccharidosis?
any one of four enzymes involved in degradation of heparin sulfate
68
What is the treatment for Mucopolysaccharidosis?
no standard treatment
69
What are the two most common Sphingolipidosis disorders?
Tay-Sachs | Gaucher
70
How is Sphingolipidosis characterized?
inability to degrade sphingolipids
71
What is the result of inability to degrade spingolipids?
accumulation of lipids or glycolipids, especially in brain, liver and spleen
72
If the CNS is involved in Sphingolipidosis, what is the progression of the disease?
mental deterioration seizures death in childhood
73
What enzyme is deficient in Tay Sachs?
B-hexosaminidase | results in accumulation of sphingolipid GM, ganglioside
74
What population has a high incidence of Tay-Sachs?
Ashkenazi Jews
75
How does Tay-Sachs present?
at 6 months with poor feeding, lethargy, eventual developmental regression and feeding difficulties Death usually occurs by 3 due to respiratory infections (less severe forms are reported)
76
How is diagnosis of Tay-Sachs aided?
cherry red spot in center of macula fundus
77
What is the treatment for Tay-Sachs?
no current treatment
78
What enzyme is deficient in Gaucher?
glucosylceramide B-glucosidase
79
What population has a high incidence of Gaucher?
Ashkenazi Jews
80
What is the most common Sphingolipidosis?
Gaucher
81
Describe Type 1 Gaucher.
``` adult onset (most common form) pain in limbs, joints and/or trunk tendency to bone fractures hepatomegaly mild anemia some changes in vertebrae CNS is spared ```
82
Describe Type 2 Gaucher.
``` presents between 3-6 months CNS involvement Failure to thrive hepatosplenomegaly developmental regression neurological deterioration **seizures Death by age 2 due to repeated respiratory infections ```
83
Describe Type 3 Gaucher.
presents in childhood with intermediate symptoms
84
How would you treat Gaucher?
Type 1/3 analgesics for pain management Splenectomy in some cases Cerezyme (enzyme replacement therapies) Type 2 no known treatment
85
List two nucleic acid disorders.
Lesch Nyhan Syndrome | Adenosine Deaminase Deficiency
86
What enzyme is deficient in Lesch Nyhan?
HGPRT (hypoxanthine guanine phosphoribosyltransferase) | - involved in salvage pathway of purine
87
What product builds up due to inability to salvage purines?
hypoxanthine guanine PRPP **also causes a feed forward reaction to de novo synthesis
88
Increased levels of PRPP causes activation of what pathway?
de novo synthesis of purines | -levels can be 200x higher
89
Breakdown of excess purines will result in accumulation of ?
uric acid
90
What results from too much uric acid?
crystals form>>>gout "sand in diaper"
91
What are the symptoms of Lesch Nyhan?
uncontrolled movements spasticity mental retardation compulsive self-mutilation
92
What is the treatment for Lesch Nyhan?
Allopurinol, but does NOT seem to treat the neurological symptoms
93
What enzyme is responsible for 15% of all cases of SCID (Severe combined immunodeficiency syndrome)?
adenosine deaminase
94
How does adenosine deaminase deficiency present?
in infancy with recurrent bacterial and viral infections **if untreated can lead to death
95
What is adenosine deaminase responsible for converting?
AMP to IMP in the purine salvage pathway
96
What immune deficiencies are seen in patients with adenosine deaminase deficiency?
deficient in T and B cells leaving them without a functional immune system
97
What is the treatment for adenosine deaminase deficiency?
no current treatment clinical trials under way using gene therapy to treat SCID
98
What is a porphyrin?
ringed structures that can chelate metal
99
List two Porphyrin Metabolism Disorders?
Acute Intermittent Porphyria | Congenital Erythropoietic Porphyria
100
What enzyme is deficient in Acute Intermittent Prophyria?
uroporphyrinogen I synthase - used in bone marrow heme synthesis - leads to increased excretion of the precursors porphobilinogen and delta-aminolevulinc acid in urine
101
What are the symptoms of Acute Intermittent Prophyria?
``` abdominal pain weakness vomiting mental and emotional disturbances anemia some: hallucinations coma ```
102
What can precipitate Acute Intermittent Prophyria?
use of certain drugs steroids anticonvulsants barbituates
103
What enzyme is deficient in Congenital Erythropoietic Porphyria?
uroporphyrinogen III synthase | - in bone marrow heme synthesis
104
What are the symptoms of Congenital Erythropoietic Porphyria?
- extreme photosensitivity - hemolytic anemia - require blood transfusions and splenectomy - red/brown discoloration of teeth, fluoresce red under UV light
105
6 month old is brought in for recurrent respiratory infection. The child seems to be moving backwards developmentally and has a history of seizures. Testing reveals a deficiency in _______ , leading to a diagnosis of _____.
glucosylceramide b-glucodidase | Gaucher

CMBM 3 (28 decks)

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