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*GIGU I > 25. Genetics of GI Disorders > Flashcards

25. Genetics of GI Disorders Flashcards

1
Q

Jaundice in the setting of elevated AST/ALT would indicate what type of etiology?

A

Hepatocellular, such as with acute viral hepatitis

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2
Q

Jaundice in the setting of elevated ALP would indicate what type of etiology?

A

Cholestasis, like with common duct stone

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3
Q

Bilirubin is considered indirect/unconjugated prior to UDP glucoronyl transferase activity in the liver, what acts as the carrier for unconjugated bili in the bloodstream?

A

Albumin

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4
Q

Enzyme deficiency of criglar-najjar syndrome

A

UDP glucuronyl transferase

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5
Q

Is criglar najjar associated with indirect or direct bili?

A

All direct/unconjugated bili

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6
Q

What is a complication of the more severe type 1 criglar najjar, characterized by encephalopathy?

A

Kernicturus

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7
Q

When does type 1 criglar najjar manifest? What are some treatments?

A

Infancy

Tx = transfusions, phototherapy, heme oxygenase inhibitors, oral calcium phosphate and carbonate, liver transplant

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8
Q

How does type 2 criglar najjar differ from type 1?

A

Benign form resulting from mutation that causes partial deficiency of gene

Presents in childhood/adolesence (vs infancy in type 1)

Can be tx with phenobarbitol (while type 1 cannot)

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9
Q

Inheritance of dubin johnson syndrome

A

Autosomal recessive

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10
Q

Is dubin johnson syndrome associated with direct or indirect bili?

A

Direct/conjugated

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11
Q

Defect in dubin johnson syndrome

What does it lead to?

A

Defect in canalicular multiple organic anion transporter Mrp2

Leads to accumulation of conjugated bili because it can no longer be exported from hepatocytes into bile

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12
Q

Dubin johnson is normally asymptomatic and benign, but it may manifest in _______ or when _______ drugs are taken (which are contraindicated)

A

Pregnancy; oral contraceptive

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13
Q

Inheritance of rotor syndrome

A

Autosomal recessive

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14
Q

What syndrome is rotor syndrome very similar to?

A

Dubin johnson; both involve impaired biliary excretion of conjugated organic anions and bilirubin, usually asymptomatic other than possible jaundice

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15
Q

How is rotor syndrome different from DJ syndrome?

A

Slow BSP elimination kinetics without secondary rise (DJ has secondary rise)

Age of onset is adolecence/early adulthood while DJ can arise earlier in childhood

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16
Q

Does gilberts disease have to do with conjugated or unconjugated bili?

A

Unconjugated

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17
Q

Is gilberts disease severe?

A

No, it is a relatively common benign disorder where serum total bili is below 6, but it may increase in the setting of lifestyle factors like alcohol use

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18
Q

Why is phenobarbitol an effective tx for gilberts disease and criglar najjar type 2?

A

The unconjugated bili that is accumulating is hydrophobic, as is the drug phenobarbitol

Phenobarbitol increases the mRNA synthesis and expression of UTG1A1, the enzyme that is affected in these two conditions

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19
Q

When does gillbert’s usually present?

A

In early adulthood, often first recognized with fasting. Mild hemolysis may be seen in some patients

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20
Q

What is the most common porphyria in the US?

A

Porphyria cutanea tarda (PCT)

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21
Q

What enzyme is defective in PCT? What effect does this have?

A

Uroporphyrinogen decarboxylase

Leads to accumulation of uroporphyrinogen III, which converts to uroporphyrinogen I and its uroporphyrin oxidation products

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22
Q

Is PCT erythropoeitic, hepatic, or both?

What are the symptoms?

A

It is hepatoerythropoeitic, resulting in photosensitivity in vesicles and bullae on skin of exposed areas; wine colored urine

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23
Q

Inheritance of PCT

A

Autosomal dominant

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24
Q

Defective enzyme in acute intermittent porphyria

What does deficiency lead to?

A

Porphobilinogen (PBG) deaminase

Deficiency leads to excessive production of ALA and PBG

25
Q

Is acute intermittent porphyria erythropoietic, hepatic, or both?

A

Hepatic, PBG deaminase is found in the liver

26
Q

Inheritance of acute intermittent porphyria

A

Autosomal dominant

27
Q

Symptoms of acute intermittent porphyria

A

Periodic attacks of abdominal pain and neuro dysfunction

28
Q

Tx for acute intermittent porphyria

A

Hemin = an iron-containing porphyrin consisting of protoporphyrin IX containing ferric (Fe3) bound by chloride ligand

Beneficial bc it inhibits ALA synthase to prevent buildup of ALA

29
Q

What disease is associated with a buildup of copper in the liver?

A

Wilson’s disease

30
Q

Inheritance of wilsons disease

A

Autosomal recessive

31
Q

Symptoms of wilson’s disease

A

Liver disease, copper deposits in eye (Kayser Fleischer rings), dementia, movement disorders

32
Q

Inheritance of hemochromatosis

A

Autosomal recessive; mutations in HFE gene

33
Q

Age of onset of hemachromatosis

A

Usually in 6th decade

34
Q

Describe hemochromatosis

A

Unregulated iron absorption d/t low levels of hepcidin, which would normally negatively regulate ferroportin in iron absorption

This results in accumulation of iron in liver, heart, pancreas, and skin

35
Q

Normal iron vs. someone with hemochromatosis

A

Normal = 3-5g

Hemochromatosis = 15g

36
Q

Symptoms of hemochromatosis

A

Cirrhosis, heart failure, DM, bronzed skin, malabsorption

37
Q

What lab technique is used to diagnose hemochromatosis?

A

PCT

38
Q

Inheritance of galactosemia

A

Autosomal recessive

39
Q

When do symptoms of classic galactosemia typically manifest?

A

When infant drinks milk

40
Q

Enzyme deficiency in classic vs. mild galactosemia

A

Classic = galactose I phosphate uridyltransferase (GALT) - catalyzes RL step in galactose metabolism

Mild form = galactokinase or UDP-galactose epimerase

41
Q

Symptoms of classic galactosemia

A

Cataracts within first few weeks of life, hepatomegaly, jaundice, FTT

42
Q

Symptoms of mild form of galactosemia

A

Galactose accumulation in blood and urine

43
Q

Hereditary fructose intolerance may result in _____ _____, or fructose in the urine

A

Essential fructosuria

44
Q

Inheritance of hereditary fructose intolerance

A

Autosomal recessive

45
Q

Enzyme deficiency in hereditary fructose intolerance and the effect this has

A

Aldolase B - typically responsible for cleaving fructose 1P into glyceraldehyde and DHAP

Results in accumulation of F1P, which sequester’s much of a cell’s phosphate, thus inhibiting glycogen phosphorylase (and thus glycogenolysis)

VIRTUALLY STOPS ATP SYNTH IN THE LIVER

46
Q

Patient presentation in hereditary fructose intolerance

A

Hypophosphatemia
Hypoglycemia
Low tolerance to foods with fructose and sucrose

Signs/symptoms manifest when infant is weaned off milk and given foods containing fructose and sucrose

May have essential fructosuria

47
Q

PEPCK deficiency inheritance and symptoms

A

Auto recessive, mutation in PEPCK1/2 that results in defective gluconeogenesis and hypoglycemia, FTT, loss of muscle tone, hepatomegaly

48
Q

Normal action of PEPCK

A

Catalyzes conversion of OAA to PEP in gluconeogenesis

49
Q

Inheritance of von gierke disease

A

Autosomal recessive

50
Q

Enzyme deficiency in von gierke Ia; what does this lead to

A

Deficient glucose 6 phosphatase - normally necessary for release of free glucose into blood by liver

Patients exhibit marked fasting hypoglycemia d/t inability to utilize glycogenolysis or gluconeogenesis

Also lactic acidosis, hepatomegaly, elevated serum TAGs, retarded growth, buildup of lactate, alanine, and glycerol

51
Q

If von gierke Ia is caused by G6Pase deficiency (catalytic unit), what causes types Ib and c?

A

Mutations in transporter part of G6Pase enzyme complex in ER membrane

52
Q

Irinotecan is a medication that should be avoided in those with which of the following?

A. Criglar Najjar
B. Gilbert’s Syndrome
C. Dubin-Johnson/Rotor’s Syndrome
D. Wilson’s disease
E. PEPCK deficiency
F. Von Gierke’s disease
A

B. Gilbert’s syndrome

53
Q

Which of the following is associated with a grossly black liver due to impaired excretion of epinephrine metabolites?

A. Criglar Najjar
B. Gilbert’s Syndrome
C. Dubin-Johnson syndrome
D. Wilson’s disease
E. PEPCK deficiency
F. Von Gierke’s disease
A

C. Dubin-Johnson syndrome

54
Q

You are evaluating a patient for possible metabolic disease and lab work shows direct hyperbilirubinemia, decreased coproporphyrin III:corproporphyrin I ratio, and elevated total urine coproporphyrin levels. What is the likely diagnosis?

A. Criglar Najjar
B. Gilbert’s Syndrome
C. Dubin-Johnson Syndrome
D. Rotor’s Syndrome
E. Wilson’s disease
A

D. Rotor’s syndrome

[same presentation as DJS, but would not get elevated urine coproporphyrin levels in DJS]

55
Q

Wilson’s disease is associated with a mutation in what gene?

A

ATP7B - encodes a transmembrane P-type ATPase used to pump copper into bile and plasma

56
Q

Inheritance of Gilbert’s disease

A

Can be AD or AR

57
Q

Inheritance of criglar najjar type 1 vs. type 2

A

Type 1 is AR

Type 2 is AD

Both are mutations in UTG1A1, as is Gilbert’s disease

[UGT1A1 is an enzyme that sticks a sugar on things to make them soluble so that they can be excreted]

58
Q

Wilson’s disease results in free copper accumulation due to mutation in ATP7B. This leads to failure of copper to enter circulation bound to ________, which is the transport protein for copper. Free copper generates free radicals that damage tissues

A

Ceruloplasmin

59
Q

Both Wilson’s disease and primary biliary cirrhosis, as well as several other conditions, may result in increased copper accumulation. How would you differentiate Wilson’s disease from things like primary biliary cirrhosis?

A

Presence of Kayser-Fleischer rings - which are RARELY seen in conditions other than Wilson’s disease

*GIGU I (67 decks)

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