Deck 29: Porphyrins and Porphyrias

Question 1

Moderate elevations of which of the following occur secondary to lead toxicity or iron-deficiency anemia?

A) Porphobilinogen
B) Protoporphyrin IX
C) ALA
D) Heme

Answer 1

ALA

Question 2

An individual with jaundice reports to the emergency department with symptoms of an acute porphyric attack,including severe abdominal pain,pain in her thighs,vomiting,and muscle weakness.A hepatitis screen is negative and unconjugated bilirubin and urobilinogen are increased.Your laboratory receives a dark orange-colored urine sample for qualitative PBG analysis,results of which are difficult to interpret.When you contact the physician with this information,the physician informs you that this patient is an alcohol abuser and asks you to run a quantitative urine porphyrin analysis.Results of this analysis show an increased uroporphyrin and coproporphyrin III.Why was the PBG difficult to interpret?

A) In individuals with congenital erythrocytic porphyria,PBG is negative.
B) There was interference from elevated urobilinogen in the urine sample.
C) PBG only demonstrates an increase in fecal samples,not in urine.
D) Alcohol in the urine sample produced a false-negative value for PBG.

Answer 2

There was interference from elevated urobilinogen in the urine sample.

Question 3

The enzyme that is an iron-sulfur protein located in the inner mitochondrial membrane that inserts ferrous iron into protoporphyrin to form heme is:

A) ferrochelatase.
B) protoporphyrin oxidase.
C) ALAS.
D) hematin.

Answer 3

ferrochelatase.

Question 4

The skin lesions observed in individuals with nonacute porphyria are caused by:

A) brain dysfunction and peripheral neuropathy.
B) excessive production of retinoic acid in the eye.
C) the excess of porphyrin intermediates in the liver.
D) the excess presence of porphyrins in the skin that generate oxygen radicals.

Question 5

An individual visits his physician with porphyria-like symptoms.The results of porphyrin analysis are as follows: urine 5-aminolevulinic acid (ALA),positive; urine coproporphyrin III,increased; RBC zinc protoporphyrin (ZPP),increased.What laboratory test should the physician order to determine the exact diagnosis?

A) Blood lead
B) Urinary PBG
C) Hemoglobin and hematocrit
D) Blood alcohol

Question 6

Protoporphyrin that contains iron is known as:

A) ferrochelatase.
B) heme.
C) porphyrin.
D) porphyria.

Question 7

Which one of the following cofactors is required for heme synthesis?

A) Ascorbic acid
B) Pyridoxal phosphate
C) Cobalamin
D) Niacin

Question 8

A physician calls the laboratory stating that one of her patients is exhibiting what she suspects to be an acute porphyric attack.The patient is having acute abdominal pains and seems apathetic and distant.If the urine test for PBG in the preceding question is strongly positive and remains elevated for 2 weeks or longer,which one of the following is the most likely disease process?

A) Lead poisoning
B) EPP
C) AIP
D) PCT

Question 9

Erythrocyte protoporphyria (EPP):

A) consists only of coproporphyrins.
B) leads to progressive hepatic failure.
C) has as its principal component coproporphyrin IX.
D) is decreased in cases of lead toxicity.

Question 10

What is the name of the oxygen storage protein found in muscle that uses heme as its prosthetic group?

A) Myoglobin
B) Hemoglobin
C) Cytochrome b1
D) Catalase

Question 11

An individual is suspected of having some type of porphyria although he has no skin lesions.The qualitative screen demonstrates an elevated PBG and ALA in urine.Upon quantitation,the PBG was noted as being more increased than the ALA.Further quantitative tests indicated increased uroporphyrin and fecal porphyrin.The plasma fluorescence emission peak was at 624 to 628 nm.What is the likely diagnosis?

A) Congenital erythropoietic porphyria (CEP)
B) Acute intermittent porphyria (AIP)
C) Variegate porphyria (VP)
D) Porphyria cutanea tarda (PCT)

Question 12

The immediate precursor of the porphyrins is:

A) ALA.
B) succinyl CoA.
C) porphobilinogen.
D) hydroxymethylbilane.

Question 13

A deficiency of the enzyme hydroxymethylbilane synthase (HMBS)results in which one of the following acute porphyrias?

A) Variegate porphyria (VP)
B) Hereditary coproporphyria (HCP)
C) Acute intermittent porphyria (AIP)
D) Porphyria cutanea tarda (PCT)

Question 14

The heme precursor that is elevated in PCT is:

A) PBG.
B) coproporphyrin.
C) uroporphyrin.
D) protoporphyrin.

Question 15

Porphyrin synthesis is regulated by modulation of which one of the following enzymes?

A) Ferrochelatase
B) ALA-dehydrase (ALAD)
C) ALA-synthase (ALAS)
D) Phorphyrinas

Question 16

In the analysis of plasma porphyrins,porphyrins at neutral pH fluoresce between 610 to 640 nm.

Question 17

An important amino acid in the synthesis of ALA is:

A) glutamine.
B) glycine.
C) cysteine.
D) methionine.

Question 18

A group of compounds containing four monopyrrole rings connected by methane bridges is the:

A) porphyrins.
B) porphyrias.
C) porphobilinogens.
D) heme precursors.

Question 19

A physician calls the laboratory stating that one of her patients is exhibiting what she suspects to be an acute porphyric attack.The patient is having acute abdominal pains and seems apathetic and distant.Initial laboratory analysis should include:

A) quantitative porphyrin analyses of all porphyrins.
B) urine ALA screen.
C) serum iron.
D) urinary PBG.

Question 20

When using DNA analysis to screen a new family to identify a genetic mutation that has caused porphyria,what must be examined?

A) A single mutation is all that needs to be assessed.
B) The entire genome of each family member must be examined.
C) A Bayesian analysis must be calculated first.
D) All exons with promoters and flanking intron sequences around the mutation must be analyzed.