Related Subjects:
|Acute Porphyrias
|Variegate Porphyria
|Acute Intermittent Porphyria (AIP)
|Porphyria Cutanea Tarda (PCT)
|Porphyria Testing
🌟 Acute Intermittent Porphyria (AIP) is the most common acute porphyria.
It is ~5x more common in females, typically presenting between ages 15–30.
Historically known as “the porphyria of King George.”
🧾 About
- Amoxicillin ✅ and opiates ✅ are thought to be safe in porphyria.
- Characterised by defective haem biosynthesis.
🧬 Aetiology
- Autosomal dominant disorder due to ↓ activity of porphobilinogen (PBG) deaminase.
- Results in accumulation of neurotoxic intermediates (PBG, δ-ALA).
⚡ Precipitants of Acute Attacks
- Fasting or surgery (catabolic stress).
- Drugs 🚫: phenobarbitone, sulphonylureas, oestrogens, OCP, alcohol.
- Other: infections, hormonal changes, stress.
🤒 Clinical Features
- Severe central abdominal pain (95% of attacks).
- GI upset: nausea, bilious vomiting, constipation/diarrhoea.
- Hypertension + tachycardia (autonomic overactivity).
- Peripheral neuropathy → motor weakness, foot drop, cranial nerve involvement.
- CNS: seizures, psychiatric disturbance, confusion, hallucinations.
- Wine-red urine during attacks (due to PBG auto-oxidation).
🚫 Drugs to avoid: Diclofenac, Alcohol, OCP, HRT, TCAs, Benzodiazepines, Barbiturates, Halothane, Cephalosporins, Sulfonamides, Macrolides, Tetracyclines, Rifampicin, Trimethoprim, Chloramphenicol, Metronidazole, ACEI, CCB, Statins, Anticonvulsants, Furosemide, Sulfonylureas, Lidocaine, Gold salts, Antihistamines, Amphetamines.
🔑 The 6 Ps of AIP
- Porphobilinogen deaminase ↓
- Pain in abdomen
- Pee discolouration (dark red urine 🍷)
- Psychiatric symptoms
- Peripheral neuropathy
- Precipitated by drugs, alcohol, Pill (OCP)
🧪 Investigations
⚠️ All samples must be protected from light.
- Bloods: Hyponatraemia common during attacks.
- Raised urinary δ-ALA and PBG (especially during attacks).
- Urine often turns port-wine colour on standing.
- Collection bottles:
- Blood – Purple (EDTA)
- Urine – White (plain 20 ml universal)
- Faeces – Blue (faecal 20 ml universal)
💊 Management
- Refer/liaise with the National Acute Porphyria Service (NAPS).
- Remove precipitants (stop unsafe drugs, correct fasting).
- IV glucose infusion (to reduce haem precursor synthesis).
- IV haem arginate (hemin) in severe attacks.
- Supportive care: fluids, pain relief (safe opiates), anti-hypertensives if needed.
📚 References
🧾 Case – Acute Intermittent Porphyria (AIP)
A 28-year-old woman presents with severe colicky abdominal pain but no peritonism.
She is tachycardic, hypertensive, and has dark urine that turns red on standing.
Over 24h she develops limb weakness. She recently started trimethoprim and has been fasting.
🧪 Key tests: ↑ urinary porphobilinogen & ALA, hyponatraemia. 👉 Diagnosis: Acute intermittent porphyria, drug + fasting triggered. 💊 Management: IV glucose, IV haem arginate, stop precipitating drugs, supportive care.
