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Erik's IHO Week 4 > 5-14 GOUELI Heme Metabolism > Flashcards

5-14 GOUELI Heme Metabolism Flashcards

1
Q

What is the rate limiting step in the synthesis of heme?

A

Glycine + Succinyl-CoA –> δ-ALA (aminolevulinic acid)

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2
Q

How is δ-ALA synthase activity regulated?

A

Negative feedback from Heme

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3
Q

What is the significance of vitamin B6 in heme synthesis?

A

It’s a cofactor for δ-ALA synthase

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4
Q

What can a vitamin B6 deficiency cause?

A

↓B6 –>↓Hb synthesis –> microcytic, hypochromic (low color) anemia

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5
Q

What is one concern with Isoniazid?

A

Isoniazid, which is Tx for TB, can –> B6 deficiency

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6
Q

What’s the site of lead toxicity in the heme synthesis pathway?

A

δ-ALA dehydratase, and ferrochelatase

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7
Q

What can lead toxicity lead to?

A

Microcytic anemia

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8
Q

What does heme positively increase production of?

A

Globin, to make hemoglobin

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9
Q

What happens to heme after RBCs die?

A

It is degraded to bilirubin

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10
Q

Where does the breakdown of heme to bilirubin occur?

A

In the RES (Reticuloendothelial system, ie spleen, macrophages, etc)

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11
Q

What happens to bilirubin in the liver?

A

It is conjugated

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12
Q

What do we mean when we say bilirubin is conjugated?

A

You’re adding UDP-glucouronate to make it more water soluble

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13
Q

What is the difference btwn direct and indirect bilirubin?

A

Direct is conjugated. Indirect is unconjugated.

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14
Q

What is the significance of direct vs indirect bilirubin?

A

If patient has jaundice (which is due to build-up of bilirubin), type of bilirubin (direct vs indirect) can help us figure out where damage is occurring

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15
Q

If patient has intravascular hemolysis (like seen in G6PD deficiency), what form will the bilirubin in her system be in?

A

Unconjugated (indirect) form b/c it hasn’t passed through liver yet

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16
Q

If patient has obstruction of biliary system, what form will the bilirubin in his system be in?

A

Conjugated bilirubin (direct) b/c it HAS passed through liver

17
Q

Define porphyria

A

A genetic deficiency in one of the enzymatic steps of the heme synthesis pathway –> disease b/c toxic accumulation of enzyme precursor

18
Q

How can you detect a porphyria in a patient?

A

Urine measurements of enzyme intermediates, particularly ALA and PBG

19
Q

What is the inheritance pattern of the porphyrias?

A

Autosomal dominant (except ALA dehydratase deficiency which is AR)

20
Q

What symptoms would you see in an acute intermittent porphyria patient?

A

Polyneuropaty
Painful abdomen
Port-colored urine (darkens b/c light oxidizes enzyme precursors)
Precipitated by drugs

21
Q

What is there long-term increased risk of in AIP patient?

A

Hepatocellular carcinoma

22
Q

How do you treat AIP?

A

Glucose and heme (IV) to inhibit heme synthesis pathway!

23
Q

What is the #1 porphyria?

A

Porphyria cutanea tarda (PCT)

24
Q

Is Porphyria cutanea tarda life-threatening?

A

No

25
Q

If you have a patient with PCT (Porphyria Cutanea Tarda), what do you need to test for?

A

Hepatitis C b/c >50% of patients are positive

26
Q

What are symptoms of PCT?

A

Photosensitivity
Hyperpigmentation
Hypertrichosis (hair growth)
Bullous dermatosis (blistering skin lesions)

27
Q

What is the pathogenesis of PCT?

A

For some reason, too much iron

↑iron –> symptoms

28
Q

What is Tx for PCT?

A

Reduce iron! Use phlebotomy or chelation

29
Q

Discuss the malleability of RBCs

A

RBCs must be very malleable to fit through tiny capillaries and handle changes in tonicity
Must also have high SA for gas exchange
Membrane composed of complex cytoskeletal system

30
Q

What are the important proteins involved in the RBC membrane cytoskeleton?

A

Ankryin
Spectrin
Actin

31
Q

What can genetic defects of the RBC membrane cytoskeletal proteins lead to?

A

Inherited hemolytic anemias

32
Q

What is hereditary spherocytosis?

A

Genetic defect in Spectrin protein -> less malleable RBCs

Less malleability –> premature RBC destruction in spleen

33
Q

Morphology of RBC in Hereditary Spherocytosis?

A

Spherocyte: RBC is more of a sphere and less concave disk

34
Q

Sx of Hereditary Spherocytosis?

A

Hemolysis & anemia
Jaundice
Splenomegaly

35
Q

Tx of Hereditary Spherocytosis?

A

Splenectomy

36
Q

How are damaged RBCs that are no longer deformable eliminated?

A

They are trapped in spleen and destroyed by macrophages

Erik's IHO Week 4 (4 decks)

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