Can you provide mnemonics to help memorize the porphyrias and their associated enzyme deficiencies?

Mnemonics for Porphyrias and Enzyme Deficiencies

Use structured mnemonics to memorize the heme biosynthesis pathway enzymes and their associated porphyrias, as imagery-based memory techniques have demonstrated superior long-term retention compared to traditional learning methods. 1

The Heme Biosynthesis Pathway Mnemonic

Enzyme Sequence: "ALAD Can't Help Undo Porphyrin Problems Forever"

This mnemonic follows the 8 enzymatic steps in order 2, 3:

1. ALA Synthase (ALAS)
2. ALA Dehydratase (ALAD)
3. Porphobilinogen deaminase (also called Hydroxymethylbilane synthase - HMBS)
4. Uroporphyrinogen III synthase
5. Uroporphyrinogen decarboxylase
6. Coproporphyrinogen oxidase
7. Protoporphyrinogen oxidase
8. Ferrochelatase

The Four Acute Hepatic Porphyrias: "ALAD Has Very Poor Attacks"

This helps remember the four AHPs and their deficient enzymes 2, 3:

• ALAD = ALA Dehydratase deficiency porphyria (ALAD-DP)

  • Enzyme: ALA dehydratase
  • Autosomal recessive, extremely rare 3

• Has = Hydroxymethylbilane Synthase deficiency = Acute Intermittent Porphyria (AIP)

  • Enzyme: HMBS (also called PBG deaminase)
  • Most common AHP, autosomal dominant 2

• Very = Variegate Porphyria (VP)

  • Enzyme: Protoporphyrinogen oxidase
  • Autosomal dominant, can have skin manifestations 3

• Poor = Hereditary CoProporphyria (HCP)

  • Enzyme: Coproporphyrinogen oxidase
  • Autosomal dominant, can have skin manifestations 3

Clinical Presentation Mnemonic: "PAINS"

For remembering acute attack symptoms 2, 4:

• Pain (severe abdominal)
• Autonomic dysfunction (tachycardia, hypertension)
• Increased porphyrin precursors (ALA and PBG)
• Neuropathy/Neuropsychiatric symptoms
• Seizures/hyponatremia

Key Distinguishing Features

Remember "VP and HCP Can See the Sun" - only Variegate Porphyria and Hereditary Coproporphyria cause chronic blistering skin lesions on sun-exposed areas, distinguishing them from AIP. 3

Diagnostic Memory Aid: "PBG is the Key"

For acute attacks, remember that urinary porphobilinogen (PBG) elevation is the critical diagnostic finding in AIP, VP, and HCP, while ALAD-DP shows elevated ALA with normal-to-slightly-increased PBG. 3, 5

Common Pitfall to Avoid

The penetrance of AIP, HCP, and VP is extremely low—over 90% of genetic mutation carriers remain asymptomatic for life, so genetic testing alone without biochemical confirmation during symptoms can lead to misdiagnosis 3. Always confirm with urinary PBG and ALA levels during acute presentations 5.