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Clin Chem > Porphyrias > Flashcards

Porphyrias Flashcards

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1
Q

What usually causes porphyrias?

A

Enzyme deficiencies in heme biosynthesis

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2
Q

Porphyrias result in the ______ and ________ of precursors in heme biosynthesis

A

overproduction and excretion

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3
Q

These are chemical intermediates in the synthesis of hemoglobin, myoglobin, and respiratory pigments

A

porphyrins

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4
Q

These are colorless and unstable metabolites of porphyrins

A

porphyrinogens

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5
Q

_______ is found in the urine of those with acute porphyria

A

Porphobilinogen

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6
Q

Urine with porphobilinogen is ______ when fresh, but then turns _______

A

normal
red/wine colored
(turns black if heated to 100 C w/ dilute HCl)

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7
Q

What are disorders of heme synthesis?

A

Porphyrias

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8
Q

Qualitative heme disorders are:

A

Hemoglobinopathies. Structural changes in globin molecule.

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9
Q

Quantitative heme disorders are:

A

Thalassemias

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10
Q

What are porphrins?

A

Stable colored compounds. Usually red-violet to red-brown.

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11
Q

Porphrins fluoresce at ________

A

400 nm

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12
Q

Protoporphyrin is…

A

Porphyrin found in feces

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13
Q

Coporporphyrin is…

A

porphyrin in urine and feces

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14
Q

Uroporphyrin is…

A

porphyrin in urine

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15
Q

Porphyrinogens are readily ______ to porphyrins upon exposure to ______ or ________

A

oxidized

light or oxygen

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16
Q

3 chemically altered hemoglobins:

A
  1. methemoglobin
  2. carboxyhemoglobin
  3. sulfhemoglobin
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17
Q

T/F Most porphyrias are due to complete lack of enzymes

A

False- most are just deficiencies of enzymes

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18
Q

Inheritance pattern of porphyrias

A

Autosomal dominant (with one exception)

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19
Q

Porphyrias can be ______ or _______

A

inherited or aqcuired

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20
Q

What is the inheritance pattern of Congenital Erythropoietic Porphyria (CEP)?

A

Autosomal recessive

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21
Q

Which porphyria is acquired?

A

Porphyria Cutanea Tarda

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22
Q

Where are the 2 main places heme precursors build up?

A

Bone marrow and liver

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23
Q

Erythropoietic porphyria is…

A

Heme precursors build up in marrow

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24
Q

Hepatic porphyria is…

A

Build up of precursors in liver

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25
Q

Acquired porphyrias can be differentiated from true porphyrias by measuring what?

A

Urinary ALA and PBG

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26
Q

Excess of early heme precursors leads to _______ porphyria

A

Neuropsychiatric

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27
Q

Excess of late heme precursors causes _______ porphyria

A

cutaneous

28
Q

What are 2 examples of early heme precursors?

A

ALA

Porphobilinogen

29
Q

What are examples of late heme precursors?

A

Uroporphyrin, Coproporphyrin, Protoporphyrin

30
Q

Regulation of this enzyme controls the rate of heme synthesis in the liver:

A

ALA synthase

31
Q

The main purpose of porphyrias in the body is…

A

to contribute to the synthesis of heme

32
Q

Disease states corresponding to enzyme deficiencies have been linked to every step of heme synthesis except:

A

ALAS

33
Q

The diagnosis of porphyrias is made by a combo of ________ , _______ , and ________ findings

A

history, physical, laboratory

34
Q

_________ is usually the presenting symptom of cutaneous porphyrias

A

Photosensitivity

35
Q

ALAD porphyria is a _____ ________ disorder

A

rare genetic

36
Q

What is the deficiency in ADP?

A

ALA dehydratase (ALAD)

37
Q

What is precursor is measured in ADP?

A

ALA in urine

38
Q

CEP stand for ______ and is a(n) ______ porphyria

A

Congenital erythropoietic porphyria; erythropoietic

39
Q

AIP stands for __________ and is a(n) ________ porphyria

A

Acute intermittent hepatic porphyria; hepatic

40
Q

HCP stands for ________ and is a(n) _______ porphyria

A

hereditary coproporphyria; hepatic

41
Q

EPP stands for _______ and is a(n) ______ porphyria

A

erythropoetic protoporphyria; hepatic

42
Q

mixed porphyrias as also known as…

A

Variegated porphyria (VP)

43
Q

Accumulation of uroporphyrinogen & coproporphyrinogen in the body tissues lead to…

A 
Excretion of these metabolites in urine & feces
Light sensitivity (tissues mutilate when exposed)
44
Q

Most common of hepatic porphyrias is:

A

PCT (porphyria cutanea tarda). However, is classified as erythropoietic due to skin manifestations

45
Q

PCT is mostly ______

A

acquired; few may be auto-dominant

46
Q

what is deficient in PCT?

A

Uroporphyrinogen decarboxylase

47
Q

Decrease in Uroporphyrinogen decarboxylase leads to increased production of:

A

Uroporphyrinogen

48
Q

Some degree of _____ damage is seem in all PCT patients

A

liver

49
Q

AIP is an ________ porphyria with a _______ _______ inheritance pattern and is due to an deficiency in _______ ______.

A

acute
autosomal dominant
PBG deaminase

50
Q

What builds up in AIP?

A

porphobilinogen & ALA

51
Q

Manifestation of AIP is mostly ________ symptoms

A

Neurological

52
Q

HCP is due to a deficiency of which enzyme?

This leads to build up of what metabolites?

A

Coproporphyrinogen oxidase

Coproporphyrinogen (III) PBG & ALA

53
Q

What is deficient in EPP?

What builds up?

A

Ferrochelatase

Protoporphyrins in plasma and feces; possibly Coproporphyrinogen

54
Q

This is the second most common porphyria

A

EPP

55
Q

EEP leads to lifelong accumulation of protoporphyrins in _____

A

skin

light sensitivity seen

56
Q

What is the most severe complication of EEP?

A

Progressive hepatic failure due to accumulation of protoporphyrins in liver

57
Q

What enzyme is deficient in VP?

A

Protoporphyrinogen oxidase

58
Q

How do we distinguish VP from EPP?

A

RBCs will fluoresce red in EPP

RBCs in VP have normal protoporphyrin levels- no fluorescence

59
Q

What is secondary porphyria and how is it distinguished from primary?

A

Secondary: Mild to moderate increase in porphyrins in urine. Not due to enzyme deficiency, but due to drugs, toxins, or other disorders.

In secondary, urinary ALA will be increased but PBG normal

60
Q

What are the 2 most common screening tests for urinary porphobilinogen?

A

Hoesch test

Watson-Schwartz test

61
Q

What is the principle of the Hoesch test?

A

Urine + Hoesch reagent

–> if PBG present, red color is formed

62
Q

What’s the principle of the Watson-Schwartz test?

A

Ehrlich reagent + sodium acetate + urine

–> If PBG present, pink pigment formed with reagent

63
Q

Generally, the cutaneous manifestations of ___ are less severe than those of ___, ___ or ___

A

EPP

PCT, VP, HCP

64
Q

These three porphyrias have neurological manifestations:

A

AIP, VP, HCP

65
Q

These porphyrias have cutaneous manifestations:

A

PCT, VP, HCP, EPP

Clin Chem (4 decks)

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