PATH - Heme synthesis, porphyrias, and lead poisoning

Question 1

Lead poisoning

Answer 1

Affected enzyme:
Ferrochelatase and
ALA dehydratase

INC Protoporphyrin, δ-ALA
(blood)

Microcytic anemia (basophilic stippling), GI and kidney disease.

Children—exposure to lead paint–>mental deterioration

Adults—environmental exposure (eg, batteries,
ammunition)–>headache, memory loss, demyelination.

Question 2

Acute intermittent porphyria

Answer 2

Affected enzyme:
Porphobilinogen deaminase

INC Porphobilinogen, δ-ALA,
coporphobilinogen
(urine)

Symptoms (5 P’s):
ƒ-Painful abdomen
ƒ-Port wine–colored urine
ƒ-Polyneuropathy
ƒ-Psychological disturbances
ƒ-Precipitated by drugs (eg, cytochrome P-450
inducers), alcohol, starvation

TX: glucose and heme

Question 3

Porphyria cutanea tarda

Answer 3

Affected enzyme:
Uroporphyrinogen decarboxylase

INC Uroporphyrin (tea-colored
urine)

Blistering cutaneous photosensitivity

Most common porphyria

Question 4

Iron poisoning

Answer 4

High mortality rate with accidental ingestion by children (adult iron tablets may look like candy)

Cell death due to peroxidation of membrane lipids

Nausea, vomiting, gastric bleeding, lethargy, scarring leading to GI obstruction.

TX: Chelation (eg, IV deferoxamine, oral deferasirox) and dialysis.