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CMBM exam 3 > Enzyme Deficiencies > Flashcards

Enzyme Deficiencies Flashcards

0
Q

Most IEMs, genetics wise are …

A

autosomal recessive or X linked recessive

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1
Q

groups of inborn errors of metabolism

A
  1. metabolites
  2. metabolic pathway
  3. Function of enzyme
  4. function of organelle
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2
Q

IEMs of amino acid metabolism

A

PKU
Oculocutaneous albinism
branched chain aa metabolism - maple syrup urine disease

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3
Q

IEMs of Carbohydrate metabolism

A

G6PDD
monosaccharide metabolism - galactosemia, hereditary fructose intolerance
glycogen storage disorders - von gierke, cori, anderson, pompe, Mcardle syndromes; hepatic phosphorylase deficiency

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4
Q

IEMs of steroid metabolism

A

congenital adrenal hyperplasia

androgen insensitivity syndrome

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5
Q

IEM of Lipid metabolism

A

familial hypercholesterolemia

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6
Q

Lysosomal storage disorders

A

mucopolysaccharidoses

sphingolipidoses

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7
Q

Purine/pyrimidine metabolism

A

Lesch Nyhan syndrome

SCID

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8
Q

IEM of Porphyrin metabolism

A

Hepatic

Erythropoietic

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10
Q

Untreated PKU (phenylketonuria) leads to

A

severe intellectual impairments and development of seizures

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10
Q

Defects in branched chain AA metabolism leads to

A

Maple syrup urine disease

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11
Q

What deficiency causes PKU?

A

defect in the enzyme Phenylalanine hydroxylase (PAH) which converts Phenylalanine into Tyrosine, results in deficiency of Tyrosine which is required for melanin synthesis
this leads to buildup of phenylalanine which then converts to phenylpyruvic acid that is excreted through urine

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12
Q

Branched chain AA?

A

Valine
Leucine
Isoleucine

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13
Q

What is the prognosis for pts with Maple syrup disease?

A

tend to be susceptible to deterioration even with dietary restriction
tend to suffer recurrent illnesses from the catabolic protein breakdown

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14
Q

What defect leads to Maple syrup disease?

A

branched chain ketoacid decarboxylase deficiency leads to Val, Leu and Ile

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15
Q

Single largest metabolic disorder?

A

Glucose 6 Phosphate dehydrogenase

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16
Q

G6PDD genetically is ….

A

X linked recessive

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17
Q

What is G6PD responsible for?

A

oxidative step of pentose phosphate pathway

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18
Q

What type of cell in G6PDD pts is most affected?

A

Red blood cells because unlike other cells doesnt have other ways to handle oxidative stress

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19
Q

with G6PDD, there is a defect in ….

A

the ability to handle oxidative damage because there is reduced ability to produce NADPH, this is a potent reducer to protect against oxidative damage

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20
Q

G6PDD Pt suffers acute oxidative damage from exposure to moth balls, what could occur?

A

Hemolytic anemia - presents as jaundice (see in newborns with G6PDD), paleness, dark urine, fatigue, shortness of breath/rapid heart rate, splenomegaly

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21
Q

Galactosemia pts are deficient in …

A

galactose 1-phosphate uridyl transferase

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22
Q

Galactosemic newborn presents with

A

vomiting, lethargy, failure to thrive and jaundice within the second week of life

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23
Q

Untreated galactosemia leads to

A

mental retardation
cataracts
liver cirrhosis

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24
Q

Hereditary Fructose intolerance is caused by?

A

deficiency in fructose-1-phosphate aldolase (Aldolase B)

leads to build up of Fructose in liver

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25
Q

Glycogen stores are largest in

A

liver and muscles

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26
Q

Congenital Adrenal Hyperplasia caused by

A

deficiency in 21-hydroxylase -90%
MCC of ambiguous genitalia in FEMALE newborns
salt losing form - presents 2-3 wks of life with circulatory collapse, hyponatremia, hyperkalemia

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27
Q

Androgen insensitivity syndrome

A

Receptor defective leaving pt unresponsive to testosterone leading to external female characteristics

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28
Q

Familial Hypercholesterolemia

A

Autosomal dominant single gene disorder

High morbidity and mortality rates via premature coronary artery disease

29
Q

Familial Hypercholesterolemia is characterized by

A

problems with the LDL receptor which leads to increased endogenous synthesis of cholesterol

30
Q

What issues can there be with receptors in FH?

A

reduced/defective biosynthesis
reduced/defective transport
abnormal binding of LDL by the receptor
abnormal internalization of the receptor

31
Q

Mucopolysaccharidoses are characterized by

A

skeletal, vascular or CNS along with coarsening of facial features

32
Q

What is Mucopolysaccharidoses due to?

A

progressive accumulation of sulfated polysaccharides

33
Q

Sanfilippo syndrome

A

Most common MPS

due to deficiency in any one of four enzymes involved in degradation of heparin sulfate

34
Q

Most common Sphingolipidoses?

A

Tay Sachs - high incidence among Ashkenazi jews

Gaucher

35
Q

Tay Sachs is due to…

A

deficiency in subunit of beta-hexosaminidase, this results in accumulation of sphingolipid GM2 ganglioside

36
Q

What is a diagnostic clue for Tay Sachs?

A

presentation of characteristic cherry red spot in the center of the macula fundus

37
Q

Gaucher is due to ….

A

glucosylceramide beta glucosidase

38
Q

Lesch Nyhan syndrome

A

Hypoxanthine guanine phophoribosyltransferase (HGPRT)

leads to increased amounts of purines - see 200x higher levels - likely due to increased amounts of PRPP

39
Q

Symptoms of Lesch Nyhan syndrome

A 
uric acid crystals 
uncontrolled movements 
spasticity 
mental retardation 
compulsive self mutilation
40
Q

Adenosine Deaminase Deficiency

A

inherited immunodeficiency

defect in adenosine deaminase - responsible for 15% of SCID - bubble boy disease

41
Q

Adenosine deaminase is responsible for …

A

conversion of AMP to IMP in purine salvage pathway

pts are severely deficient in both T and B cells, leaving them without functional immune system

42
Q

Porphyrins are …

A

ringed structures which can chelate metal ions

43
Q

What are the two main phorphyrin functions?

A

liver - cytochromes in ETC and detox of substances

Erythrocytes - hemoglobin

44
Q

Acute Intermittent Porphyria

A

due to deficiency uroporphyrinogen I synthase which leads to increased excretion of precursors porphobilinogen and S-aminolevulinic acid in urine

45
Q

Congenital Erythropoietic Porphyria characterized by

A

extreme photosensitivity
hemolytic anemia - most require multiple blood transfusions and splenectomy
Red/brown discoloration of teeth which fluoresce red under UV light

46
Q

Congenital Erythropoietic porphyria due to

A

deficiency in uroporphyrinogen III synthase

see build up of reticulocytes since body in need of RBCs

47
Q

is there an effective treatment for PKU?

A

supplementation with PAH prove ineffective
infant and child pts with PKU keep to strict diet low in phenylalanine
after normal neural development can relax dietary restrictions

48
Q

Oculocutaneous albinism results from . . . .

A

a deficiency of tyrosinase which converts Tyrosine to Melanin

49
Q

Phenotype of Oculocutaneous albinism?

A

no melanin production leads to lack of pigment in hair, skin, iris, and ocular fundus of patients

50
Q

What results from the lack of pigment seen in OCA?

A

leads to poor visual acuity, nystagmus (pendular eye movements) and underdevelopment of fovea

51
Q

What characterizes OCA type 1?

A

mutation within tyrosinase gene on chromosome 11q

classic albinism - no measurable tyrosinase activity

52
Q

What characterizes OCA type 2?

A

due to mutation in P gene (mouse homolog called pink eye) on chromosome 15q

53
Q

Newborns with Maple syrup urine disease present with?

A

first week of life with vomiting, alternating tone
if left untreated, then leads to death within a few weeks
treatment involves dietary restriction of intake of V, I and L

54
Q

What are some sources of oxidative damage?

A

infection - colds and flu
Drugs - NSAIDS, quinolones, sulfa drugs, tylenol, drugs metabolized through liver, naphtalene (moth balls) and artifical food coloring
Foods - fava beans and other legumes, sulfites, menthol-containing foods

55
Q

Acute oxidative damage in pt with G6PDD can lead to …

A

hemolytic anemia which presents with paleness, jaundice, dark urine, fatique, shortness of breath/rapid heart rate, splenomegaly

56
Q

G6PDD is genetically …

A

very diverse - more than 100 different mutations identified

57
Q

symptoms of Hereditary fructose intolerance

A

presentation age varies depends on when foods with fructose are introduced into diet
minimal to severe - failure to thrive, vomiting, jaundice, seizures

58
Q

Von Gierke disease

A

glucose 6 phosphatase

59
Q

Cori disease

A

amylo-1,6 glucosidase ( debrancher enzyme)

60
Q

Anderson disease

A

glycogen brancher enzyme (synthesis enzyme)

impairs ability to build storage

61
Q

Hepatic phosphorylase deficiency

A

multimeric enzyme complex with subunits coded for by autosomal and X linked genes

62
Q

How does Von Gierke disease present?

A

hepatomegaly (seen when glycogen stores cannot be broken down)
hypoglycemia in infants presents as sweating, fast heart rate

63
Q

How does Cori disease present?

A

hepatomegaly

muscle weakness

64
Q

How does Anderson disease present?

A

hypotonia, abnormal liver function within first year of life, progresses to liver failure quickly

65
Q

How does Hepatic phosphorylase deficiency present?

A

hepatomegaly
hypoglycemia
failure to thrive

66
Q

Which glycogen storage disease affects the liver and has no effective treatment?

A

Anderson disease

67
Q

Pompe disease

A

glycogen storage disease that affects muscle

due to deficiency in lysosomal enzyme alpha 1,4 glucosidase which is necessary for glycogen breakdown

68
Q

McArdle Disease

A

due to deficiency in muscle phosphorylase

necessary for breakdown of muscle glycogen during exercise

69
Q

symptoms of Pompe disease

A

presents in infancy with hypotonia, delay in gross motor milestones, due to muscle weakness,
eventually leads to enlarged heart and death from cardiac failure within first 2 years
no current treatment

70
Q

symptoms of McArdle

A

presents in adolescence with muscle cramps during exercise

no effective treatmetn

CMBM exam 3 (24 decks)

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