14. Porphyrins and Hemoglobin

Question 1

What are porphyrias?

Answer 1

Disorders that result from a buildup of natural chemicals that produce porphyrin in your body. They are metabolic disorders of heme synthesis, characterized by increased excretion of porphyrins or porphyrin precursors.

Porphyrins are essential for the function of hemoglobin — a protein in your red blood cells that links to porphyrin, binds iron, and carries oxygen to your organs and tissues.

Question 2

What is the difference between acute porphyrias and non-acute porphyrias?

Answer 2

There are two general categories of porphyria: acute, which mainly affects the nervous system, and cutaneous (non-acute), which mainly affects the skin. Some types of porphyria have both nervous system symptoms and skin symptoms.

Question 3

Porphyrias are inherited, acquired, or can be both?

Answer 3

Porphyrias can be inherited or acquired

Question 4

What is the most common reason for a patient to get an acquired form of porphyria?

Answer 4

Due to lead poisoning.

Question 5

Porphyrias can be classified into two groups:

Answer 5

1. Erythropoietic (enzyme deficiency/defect in erythrocytes)

2. Hepatic (enzyme deficiency/defect in liver)

Question 6

What are the 4 types of hepatic porphyria?

Answer 6

1. Acute intermittent porphyria
2. Porphyria cutanea tarda
3. Hereditary coproporhyria
4. Variegate porphyria

Question 7

Acute intermittent porphyria: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features, acute or non-acute?

Answer 7

Hepatic

Enzyme defect: Uroporhyrinogen I synthase (porphobilinogen deaminase)

Increased excretion of porphobilinogen PBG) and ALA

Features: urine darkens on exposure to air, abdominal pain and neuropsychiatric symptoms (NO PHOTOSENSITIVITY)

Question 8

Which porphyria has enzyme defect: Uroporhyrinogen I synthase (porphobilinogen deaminase)

Answer 8

Acute intermittent porphyria

Question 9

Porphyria cutanea tarda: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features?

Answer 9

Hepatic

Enzyme defect: Uroporphyrinogen decarboxylase

Increased excretion of uroporhyrins I and III and rarely porphobilinogen

Features: only photosensitivity

Question 10

Which porphyria is most common?

Answer 10

Porphyria cutanea tarda

Question 11

Which porphyria is associated with liver damage caused by alcohol consumption or iron overload?

Answer 11

Porphyria cutanea tarda

Question 12

Hereditary coproporhyria: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features?

Answer 12

Hepatic

Enzyme defect: Coproporphyrinogen oxidase

Increased excretion of Coprophyrinogen III and other intermediates prior

Features: abdominal pain, photosensitivity, neuropsychiatric symptoms

Question 13

Variegate porphyria: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features?

Answer 13

Hepatic

Enzyme defect: Protoporphyrinogen oxidase

Almost all intermediates accumulate in body and excreted in urine and feces

Features: abdominal pain, photosensitivity, neuropsychiatric symptoms

Question 14

What are the 2 types of erythropoietic porphyrias?

Answer 14

1. Congenital erythropoietic porphyria

2. Protoporphyria

Question 15

Congenital erythropoietic porphyria: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features?

Answer 15

Erythropoietic

Enzyme defect: Uroporphyrinogen III cosynthase

Increased excretion of uroporphyrinogen I (hydroxymethylbilane)

Characteristic features: photosensitivity and hemolysis

Question 16

What is another name for Congenital erythropoietic porphyria (CEP)?

Answer 16

Günther disease

Question 17

What is the rarest porphyria?

Answer 17

Congenital erythropoietic porphyria (CEP), also known as Günther disease

Question 18

Protoporphyria: hepatic or erthyropoietic, enzyme defect, increased excretion of what, characteristic features

Answer 18

Erythropoietic

Enzyme defect: Ferrochelatase

Increased excretion of protoporphyrin IX

Characteristic features: photosensitivity, reticulocytes (young RBCs) and skin biopsy show red fluorescence

Question 19

Acquired or toxic porphyria is caused by what?

Answer 19

Due to exposure of heavy metals and toxic compounds and drugs that inhibits many enzymes in heme synthesis.

Question 20

Which heme precursors are excreted almost exclusively in the urine?

Answer 20

ALA, Uroporphyrinogen, PBG, are water soluble

Question 21

Which heme precursors are excreted almost exclusively in the feces?

Answer 21

Protoporphyrin and protoporphyrinogen

Question 22

What are the 3 different tests for porphyrinogen?

Answer 22

1. Ehlrichs Test
2. Watson Schwartz test
3. Hoesch’s test

Question 23

What does the Ehlrich test detect?

Answer 23

Urobilinogen

Question 24

What does the Watson Schwartz and Hoesch test detect?

Answer 24

Porphobilinogen

Question 25

To test for total porphyrins in urine and feces, and EDTA blood sample, what method is used?

Answer 25

Spectrophotometry