Related Subjects:
|Acute Porphyrias
|Variegate Porphyria
|Acute Intermittent Porphyria (AIP)
|Porphyria Cutanea Tarda (PCT)
|Porphyria Testing
π©Έ Acute porphyrias are hereditary disorders of haem biosynthesis (prevalence ~1 in 75,000). They can cause severe, potentially life-threatening neurovisceral attacks.
β οΈ The BNF advises: if no safe alternative exists, essential drug treatment should not be withheld even in patients with acute porphyria.
π About
- π Disruption of the haem synthetic pathway.
- β οΈ Accumulation of haem precursors causes neurotoxicity and systemic symptoms.
- π Extreme care required when prescribing β always check safe drug lists.
π National UK Links
𧬠Types of Acute Porphyria
Type |
Details |
π©Ί Acute Intermittent Porphyria (AIP) |
Most common. Deficiency of porphobilinogen deaminase. Presents with abdominal pain, neuropsychiatric features, and autonomic dysfunction. |
βοΈ Hereditary Coproporphyria (HCP) |
Deficiency of coproporphyrinogen oxidase. Similar to AIP but can cause photosensitivity. |
π Variegate Porphyria (VP) |
Deficiency of protoporphyrinogen oxidase. Acute neurovisceral attacks + blistering photosensitivity. |
π§ͺ ALAD Deficiency Porphyria (ADP) |
Rare. Deficiency of delta-ALA dehydratase. Mainly neurological symptoms. |
β οΈ Precipitants
- π Unsafe drugs (barbiturates, sulfonamides, hormonal contraceptives).
- π· Alcohol, π« fasting, π©Έ hormonal changes (e.g. menstruation).
- π¦ Infection, stress, dehydration.
π« Drugs to Avoid (check full list in BNF/UKPMIS)
- β Barbiturates
- β Sulfonamides, Co-trimoxazole
- β Tricyclics & MAOIs
- β Hormonal contraceptives, HRT
- β Imidazole & Triazole antifungals (oral/IV)
- β Protease inhibitors, NNRTIs
- β Taxanes, Cytotoxics
- β Diclofenac, Rifampicin, Metronidazole, Chloramphenicol
π©Ί Clinical Features
- π΄ Severe abdominal pain (pain out of proportion to exam).
- π§ Neurological: weakness (may involve respiratory muscles), delirium, psychosis, hallucinations, progressive paralysis.
- β€οΈ Autonomic: tachycardia, hypertension.
- π΅ Fatigue, constipation, irritability.
- βοΈ VP/HCP: blistering photosensitive skin lesions.
- π§ͺ Urine: dark red-brown colour during attacks.
π Investigations
Test | Use |
π§ͺ Urine PBG | Most important initial test β elevated in AIP attacks. |
π§ͺ Urine ALA | Also elevated during acute attacks. |
π‘ Plasma fluorescence | Diagnostic for VP & HCP under UV light. |
π© Stool porphyrins | Helps confirm VP/HCP. |
𧬠Genetic testing | Confirms mutation and porphyria subtype. |
π§ͺ Enzyme activity | Useful in AIP (PBG deaminase deficiency). |
π©Ί LFTs | Assess hepatic involvement and monitor long-term risks (HCC). |
π Treatment: In the UK, haem arginate (hemin) is given IV during acute crises (via NAPS at Cardiff or Kingβs College London). IV dextrose is also used to suppress haem synthesis.
π οΈ Management (UK Practice)
- π Emergency: ABC, monitoring, admit to quiet darkened room.
- β Stop precipitating drugs/triggers.
- π IV glucose (to suppress ALA synthase).
- π©Έ IV haem arginate via NAPS for severe/prolonged crises.
- π Symptom relief: opioids for pain, antiemetics, beta-blockers for tachycardia.
- π§Ύ Long-term: trigger avoidance, liver monitoring (β HCC risk), genetic counselling.
π‘οΈ Prevention
- π« Avoid alcohol, starvation, unsafe drugs.
- βοΈ For VP/HCP: avoid sun exposure, use high-factor sunscreen.
- π©Ί Regular liver surveillance for hepatocellular carcinoma.
π References