Porphyrias

Question 1

Porphyria: AIP
Defective Enzyme 
Substrate Accumulation 
Substrate Causes 
Toxicity Symptoms 
Treatment

Answer 1

Acute Intermittent Porphyria

Defective Enzyme: PBG-Deaminase

Substrate Accumulation: Porphobilogen

Substrate Causes: increased solubility

Toxic Symptoms:

• Increased risk for liver disease
• peripheral neuropathy and neurosis real symptoms
• periodic attack of abdominal colic GI disturbances
• paralysis
• psychiatric disorders

Treatment:
-Hematin/Hemin
-Glucose
(Inhibit ALAS–decrease new synthesis to prevent more substrate accumulating)

Question 2

Porphyria: PCT
Defective Enzyme 
Substrate Accumulation 
Substrate Causes 
Toxicity Symptoms 
Treatment

Answer 2

Porphyria Cutanea Tarda
Defective Enzyme: Uroporphyrinogen decarboxylase
Substrate Accumulation: Uroporphyrinogen
Substrate Causes: photosensitivity and cutaneous symptoms

Toxicity Symptoms: risk of liver disease

• blister formation
• hypertrichosis for skin with highest sun exposure

Treatment:

• reduce sun exposure/sunscreen
• phlebotomy, chelation: reduce Fe2+ stores—>reduce uroporphyrinogen decarboxylase inhibition—>decrease substrate accumulation

Question 3

Porphyria: EP 
Defective Enzyme 
Substrate Accumulation 
Substrate Causes 
Toxicity Symptoms 
Treatment

Answer 3

Porphyria: Erythropoietic Protoporphyria
Defective Enzyme: Ferrochelatase
Substrate Accumulation: Protoporphyrin IX
Substrate Causes: photo sensitivity and cutaneous symptoms
Toxicity Symptoms: severe cutaneous photosensitivity
-burning, stinging pain with sunlight, subsequent skin changes
Treatment: sun avoidance only