[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Acute intermittent porphyria [Conditions](https://durgical.com/en/conditions/) · [Metabolism: heme, bilirubin and iron](https://durgical.com/en/conditions/) # Acute intermittent porphyria An inherited liver disorder that causes attacks of severe abdominal pain, weakness and confusion when something drives heme synthesis. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Liver](https://durgical.com/en/anatomy/liver/) - [Jejunum](https://durgical.com/en/anatomy/jejunum/) - [Ileum](https://durgical.com/en/anatomy/ileum/) - [Kidneys](https://durgical.com/en/anatomy/kidney/) - [Urinary bladder](https://durgical.com/en/anatomy/urinary-bladder/) - [White matter](https://durgical.com/en/anatomy/white-matter-of-telencephalon/) - [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/) ## In biochemistry - [Heme synthesis: Step 3 · Porphobilinogen deaminase (hydroxymethylbilane synthase)](https://durgical.com/en/biochemistry/pathways/heme-synthesis/#paso-3) - [ALA synthase](https://durgical.com/en/biochemistry/enzymes/ala-synthase/) - [ALA dehydratase](https://durgical.com/en/biochemistry/enzymes/ala-dehydratase/) - [Porphobilinogen deaminase](https://durgical.com/en/biochemistry/enzymes/porphobilinogen-deaminase/) - [Heme](https://durgical.com/en/biochemistry/molecules/heme/) - [Porphobilinogen](https://durgical.com/en/biochemistry/molecules/porphobilinogen/) - [δ-Aminolevulinic acid (ALA)](https://durgical.com/en/biochemistry/molecules/aminolevulinic-acid/) ## What it is Acute hepatic porphyria caused by partial (about 50 %) deficiency of porphobilinogen deaminase (HMBS gene). It is the most common acute porphyria. ## Who gets it Carriers of an HMBS variant are relatively common, but few ever have attacks; these occur mostly in women aged 15 to 45. In Colombia and Latin America it is rare and often diagnosed late, after repeated visits for abdominal pain. ## Causes - Autosomal dominant inheritance with low penetrance - An attack needs a trigger that induces liver ALAS1 ## Risk factors - Porphyrinogenic drugs (barbiturates, some anticonvulsants, sulfonamides) - Fasting, very low-calorie diets - Luteal phase of the menstrual cycle, progestins - Alcohol, smoking, infection, surgery and stress ## Pathophysiology With half the enzyme the pathway copes at rest. When a trigger induces ALAS1, porphobilinogen deaminase becomes a bottleneck: ALA and porphobilinogen build up and injure the autonomic, peripheral and central [nervous system](https://durgical.com/en/anatomy/system/nervous-system/). Because the block lies before porphyrins form, there is no photosensitivity. ## Classification - Latent carrier (no attacks) - Sporadic attacks - Recurrent attacks (4 or more a year) ## Symptoms and signs - Severe, diffuse abdominal pain with a near-normal abdominal exam - Nausea, vomiting and constipation - Tachycardia and hypertension - Reddish or dark urine that darkens further on standing - Mainly proximal muscle weakness and limb pain - Anxiety, insomnia, confusion or hallucinations ## Red flags - Weakness spreading to the respiratory muscles - Severe hyponatremia or seizures - Arrhythmias ## Diagnosis **Clinical** Unexplained abdominal pain with autonomic, neurological or psychiatric signs in a young woman, especially after a new drug or fasting. **Tests** Porphobilinogen and ALA in a spot urine (markedly high in an attack), adjusted for creatinine; serum sodium (hyponatremia is common); red-cell PBG deaminase activity and HMBS gene testing to confirm and screen relatives. **Imaging** There are no typical findings; abdominal CT or ultrasound rules out other causes of acute [abdomen](https://durgical.com/en/anatomy/region/abdomen/), and brain MRI looks for posterior reversible encephalopathy if there are seizures. ## Treatment **Acute** Hospital admission, removal of triggering drugs and factors, and pain control with porphyria-safe analgesics **Medical** Intravenous hemin, which represses ALAS1 and shortens the attack **Medical** Glucose (carbohydrate) loading for a mild attack or while hemin is awaited **Medical** Givosiran, an interfering RNA that silences ALAS1, for recurrent attacks **Surgical** [Liver](https://durgical.com/en/anatomy/liver/) transplantation in severe cases that do not respond **Follow-up** Monitoring of [kidney](https://durgical.com/en/anatomy/kidney/) function and periodic liver ultrasound for hepatocellular carcinoma risk ## Complications - Respiratory paralysis - Chronic neuropathy - Hypertension and chronic kidney disease - Hepatocellular carcinoma ## Prognosis With early diagnosis and hemin most patients recover fully; severe weakness may take months to improve. ## Prevention - Checking porphyria drug-safety lists - Avoiding prolonged fasting and alcohol - Genetic testing of relatives ## Test yourself Think of the answer, then tap the question to see it. ## Which enzyme fails in acute intermittent porphyria? Porphobilinogen deaminase (hydroxymethylbilane synthase), HMBS gene. ## Why does acute intermittent porphyria not cause skin lesions? The block is before porphyrins form: ALA and porphobilinogen build up, and they are not photosensitising. ## Which first-line test is ordered when an attack is suspected? Porphobilinogen in a spot urine; it is markedly raised during an attack. ## How does hemin work in an attack? It restores liver heme, which represses ALAS1 and lowers ALA and porphobilinogen production. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/acute-intermittent-porphyria/) ## Related conditions - [Lead poisoning](https://durgical.com/en/conditions/lead-poisoning/) - [Porphyria cutanea tarda](https://durgical.com/en/conditions/porphyria-cutanea-tarda/) - [Hepatocellular carcinoma](https://durgical.com/en/conditions/hepatocellular-carcinoma/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Porphyria: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/porphyria/) (MedlinePlus, US National Library of Medicine, 2026); [HMBS gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/hmbs/) (MedlinePlus, US National Library of Medicine, 2026); [Porphyria: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001208.htm) (MedlinePlus, US National Library of Medicine, 2026); [Porphyrins urine test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003614.htm) (MedlinePlus, US National Library of Medicine, 2026). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/acute-intermittent-porphyria/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/acute-intermittent-porphyria/