Practice Essentials
Acute intermittent porphyria (AIP) is one of the porphyrias, a group of hereditary diseases that involve defects in heme metabolism and result in excessive secretion of porphyrins and porphyrin precursors. [1] AIP manifests as episodes of abdominal pain, neuropathies, and constipation. Unlike some other acute porphyrias, AIP does not manifest as sun sensitivity and skin rashes.
The diagnosis of AIP can be confirmed by finding an elevated level of porphobilinogen (> 6 mg/L) on a spot urine test during an acute attack (see Workup).
Treatment options in AIP are as follows:
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Avoidance of precipitating factors (eg, fasting, unsafe drugs; see Etiology)
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High doses of glucose for mild attacks
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Hematin for severe attacks, especially those with severe neurologic symptoms
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During attacks, which generally last for several days, symptomatic treatment for pain and other manifestations (eg, tachycardia, nausea and vomiting, seizures)
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Gonadotropin-releasing hormone analogues for women with attacks related to their menstrual cycles
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Prophylactic hematin infusions
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Givosiran, in patients with acute hepatic porphyria, to decrease the rate of acute attacks [2]
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Liver transplantation, as a last resort for patients with intractable recurrent attacks that are life-threatening or severely affect quality of life
See Treatment and Medication.
For more information on the porphyrias, see Porphyria Overview.
Pathophysiology
AIP is an autosomal dominant disease that, like all forms of porphyria, is due to disruption of the pathway for the synthesis of heme. Specifically, AIP results from defects in the enzyme porphobilinogen deaminase (PBGD; also known as hydroxymethylbilane synthase [HMBS]), which catalyzes the conversion of porphobilinogen to hydroxymethylbilane. Impaired function of PBGD leads to the accumulation of the porphyrin precursors porphobilinogen and amino-levulinic acid (ALA). The predominant clinical problem appears to be neurologic damage that leads to peripheral and autonomic neuropathies and psychiatric manifestations. [3]
Although levels of porphobilinogen and ALA are always elevated during acute attacks, how this leads to the symptomatic disease is still unclear because most patients with the genetic defect have excessive porphyrin secretion but no symptoms.
A case-control study in 50 patients by Storjord et al found evidence that AIP is associated with systemic inflammation. Levels of prealbumin, C-peptide, and insulin, along with measures of kidney function, were all decreased in symptomatic patients, but not in asymptomatic ones. The decrease in C-peptide levels in symptomatic AIP cases indicates that reduced insulin release is associated with enhanced disease activity and reduction in kidney function. [4]
Etiology
Acute intermittent porphyria (AIP) is due to a combination of a genetic defect—mutations in the HMBS (hydroxymethylbilane synthase) gene that encodes the enzyme porphobilinogen deaminase [5] —and acquired factors. In patients with AIP, the function of porphobilinogen deaminase is only 40-60% of normal. With the advent of molecular technique, it has become clear that carriage of the genetic defect is much more common than symptomatic AIP. On average, out of 100 patients with the genetic defect, perhaps 10-20 secrete excess porphyrin precursors and only 1-2 have symptoms.
The classic inducers of porphyria attacks are chemicals or situations that boost heme synthesis. This includes fasting and many medications. Although very large lists of "safe" and "unsafe" drugs exist, many of these are based on anecdotes or laboratory evidence and do not meet strict criteria. In general, drugs that lead to increased activity of the hepatic P450 system, such as phenobarbital, sulfonamides, estrogens, and alcohol, are associated with porphyria. See the tables below. A large and detailed list is available on the University of Queensland, Department of Medicine Web site. However, many attacks occur without any obvious provocation.
Table 1. Drugs Thought Unsafe in Porphyria† (Open Table in a new window)
Alcuronium *Alphaxalone Alphadolone Alprazolam Aluminium Preparations Amidopyrine Aminoglutethimide Aminophylline Amiodarone *Amitriptyline [Amphetamines] *Amylobarbitone Antipyrine *Auranofin *Aurothiomalate Azapropazone Baclofen *Barbiturates *Bemegride Bendrofluazide Benoxaprofen Benzbromarone [Benzylthiouracil] [Bepridil] Bromocriptine Busulphan *Butylscopolamine Captopril *Carbamazepine *Carbromal *Carisoprodol [Cefuroxime] [Cephalexin] [Cephalosporins] [Cephradine] [Chlorambucil] *Chloramphenicol *Chlordiazepoxide *Chlormezanone Chloroform *Chlorpropamide Cinnarizine Clemastine [Clobazam] [Clomipramine HCl] [Clonazepam] Clonidine HCl *Clorazepate Cocaine [Colistin] Co-trimoxazole |
Cyclophosphamide Cycloserine Cyclosporin Danazol *Dapsone Dexfenfluramine Dextropropoxyphene Diazepam *Dichloralphenazone *Diclofenac Na Dienoestrol Diethylpropion Dihydralazine *Dihydroergotamine Diltiazem *Dimenhydrinate *Diphenhydramine [Dothiepin HCl] Doxycycline *Dydrogesterone *Econazole NO3 *Enalapril Enflurane *Ergot compounds Ergometrine maleate Ergotamine tartrate *Erythromycin *Estramustine Ethamsylate *Ethanol Ethionamide *Ethosuximide *Ethotoin Etidocaine Etomidate Fenfluramine *Flucloxacillin *Flufenamic acid Flunitrazepam Flupenthixol Flurazepam *Frusemide *Glibenclamide *Glutethimide *Glipizide Gramicidin *Griseofulvin [Haloperidol] *Halothane *Hydantoins *Hydralazine *Hydrochlorothiazide *Hydroxyzine Hyoscine *Imipramine Iproniazid Isometheptene mucate [Isoniazid] Kebuzone Ketoconazole *Levonorgestrel Lignocaine *Lisinopril Loprazolam Loxapine *Lynestrenol Lysuride |
Maleate Maprotiline HCl Mebeverine HCl *Mecillinam *Medroxyprogesterone [Mefenamic acid] Megestrol acetate *Mephenytoin Mepivacaine *Meprobamate Mercaptopurine Mercury compounds Mestranol [Metapramine HCl] Methamphetamine Methohexitone [Methotrexate] [6] Methoxyflurane Methsuximide *Methyldopa *Methylsulphonal *Methyprylone Methysergide *Metoclopramide Metyrapone Mianserin HCl Miconazole [Mifepristone] Minoxidil *Nandrolone *Nalidixic acid Natamycin *Nandrolone [Nicergoline] *Nifedipine *Nikethamide Nitrazepam *Nitrofurantoin Nordazepam Norethynodrel *Norethisterone [Nortriptyline] Novobiocin *Oral contraceptives *Orphenadrine Oxanamide [Oxazepam] Oxybutynin HCl Oxycodone *Oxymetazoline *Oxyphenbutazone Oxytetracycline Paramethadione Pargyline *Pentazocine Perhexiline Phenacetin Phenelzine *Phenobarbitone Phenoxybenzamine *Phensuximide Phenylhydrazine *Phenytoin Pipebuzone Pipemidic Acid Piritramide *Piroxicam |
*Pivampicillin *Pivmecillinam Prazepam Prenylamine *Prilocaine *Primidone [Probenecid] *Progesterone Progabide Promethazine [Propanidid] *Pyrazinamide Pyrrocaine Quinalbarbitone Rifampicin Simvastatin Sodium aurothiomalate Sodium oxybate [Sodium valproate] *Spironolactone Stanozolol Succinimides *Sulfacetamide *Sulfadiazine *Sulfadimidine *Sulfadoxine *Sulfamethoxazole *Sulfasalazine *Sulfonylureas Sulfinpyrazone Sulpiride Sulthiame Sultopride *Tamoxifen *Terfenadine Tetrazepam *Theophylline *Thiopentone Na Thioridazine Tilidate Tinidazole *Tolazamide *Tolbutamide Tranylcypromine Trazodone HCl Trimethoprim [Trimipramine] Troxidone Valproate Valpromide Veralipride *Verapamil *Vibramycin Viloxazine HCl [Vinblastine] [Vincristine] Zuclopenthixol |
*These drugs have been associated with acute attacks of porphyria. †Bracketed [] drugs are those in which experimental evidence of porphyringenicity is conflicting. |
Table 2. Drugs Thought Safe in Porphyria* (Open Table in a new window)
Acetazolamide acetylcholine Actinomycin D [6] Acyclovir Adenosine monophosphate Adrenaline Alclofenac Allopurinol Alpha tocopheryl Acetate Amethocaine Amiloride Aminocaproic acid Aminoglycosides Amoxicillin Amphotericin Ampicillin Ascorbic acid Aspirin Atenolol Atropine Azathioprine Beclomethasone Benzhexol HCl Beta-carotene Biguanides [Bromazepam] Bromides Buflomedil HCl Bumetanide Bupivacaine Buprenorphine Buserelin Butacaine SO4 Canthaxanthin Carbimazole [Carpipramine HCl] Chloral hydrate [Chlormethiazole] [Chloroquine] [Chlorothiazide] Chlorpheniramine Chlorpromazine Ciprofloxacin Cisapride Cisplatin Clavulanic acid Clofibrate Clomiphene Cloxacillin Co-codamol Codeine phosphate Colchicine [Corticosteroids] Corticotrophin (adrenocorticotropic hormone [ACTH]) |
Coumarins Cyclizine Cyclopenthiazide Cyclopropane [Cyproterone acetate] Danthron Desferrioxamine Dexamethasone [Dextromoramide] Dextrose Diamorphine Diazoxide Dicyclomine HCl Diflunisal Digoxin Dihydrocodeine Dimercaprol Dimethicone Dinoprost Diphenoxylate HCl Dipyridamole [Disopyramide] Domperidone Doxorubicin HCl Droperidol [Estazolam] Ethacrynic acid Ethambutol [Ethinyl oestradiol] Ethoheptazine citrate Etoposide Famotidine Fenbufen [Fenofibrate] Fenoprofen Fentanyl Flucytosine Flumazenil Fluoxetine HCl Flurbiprofen Fluvoxamine Maleate Folic acid Fructose Fusidic acid Follicle-stimulating hormone Gentamicin Glafenine Glucagon Glucose Glyceryl trinitrate Goserelin Guanethidine Guanfacine HCl Haem arginate [Haloperidol] Heparin Heptaminol HCl Hexamine [Hydrocortisone] Ibuprofen Indomethacin Insulin Iron Josamycin [Ketamine] |
Ketoprofen Ketotifen Labetalol Luteinizing hormone–releasing hormone Liquorice Lithium Salts lofepramine Loperamide [Lorazepam] Magnesium-sulphate [Mebendazole] Mecamylamine Meclofenoxate HCl Meclozine Mefloquine HCl [Melphalan] Meptazinol Mequitazine Metformin Methadone [Methotrimeprazine] Methylphenidate Methyluracil Metipropranolol Metopimazine Metoprolol [Metronidazole] [Midazolam] Minaprine HCl Minaxolone Morphine Nadolol Naftidrofuryl Oxalate [Naproxen sodium] Natamycin Nefopam HCl Neostigmine Netilmicin Niflumic acid Nitrous oxide Norfloxacin Ofloxacin Oxolinic acid Oxybuprocaine [Oxyphenbutazone] Oxytocin [Pancuronium bromide] Paracetamol Paraldehyde Parapenzolate Br Penicillamine Penicillin Pentolinium Pericyazine Pethidine Phenformin Phenoperidine Phentolamine mesylate Pipotiazine |
Palmitate Piracetam Pirbuterol Pirenzepine Pizotifen [Prazosin] [Prednisolone] Primaquine Probucol Procainamide HCl Procaine Prochlorperazine Proguanil HCl Promazine Propantheline Br Propofol Propranolol Propylthiouracil [Proxymetacaine] Pseudoephedrine HCl Pyridoxine [Pyrimethamine] Quinidine Quinine [Ranitidine] Reserpine Resorcinol Salbutamol Senna Sodium bromide Sodium ethylenediaminetetraacetic acid Sodium fusidate Sorbitol Streptomycin Sulbutiamine Sulindac Sulfadoxine Suxamethonium Talampicillin Temazepam Tetracaine [Tetracyclines] Thiouracils Thyroxine Tiaprofenic acid Ticarcillin Tienilic acid Timolol maleate Tolazoline Tranexamic acid Triacetyloleandomycin Triamterene Triazolam [Trichlormethiazide] Trifluoperazine Trimeprazine Tartrate Trimetazidine HCl Tripelennamine Tubocurarine Vancomycin [Vincristine] Vitamins Warfarin sodium Zidovudine Zinc preparations |
*Bracketed [] drugs are those in which experimental evidence of porphyrin genicity is conflicting. |
Epidemiology
Frequency
Estimates of the prevalence of AIP in the United States vary from 1-5 cases per 100,000 population. European studies indicate that the prevalence of AlP is approximately five per 100,000 population. [7] The prevalence can be as high as 60-100 cases per 100,000 population in northern Sweden. [8] In Japan, the prevalence of acute hepatic porphyria (most of which is AIP) is estimated to be 1.18 cases per 100 000 population. [9]
Sex- and Age-related Demographics
In most series, AIP affects women more than men, with a ratio of 1.5-2:1.
Most patients become symptomatic at age 18-40 years. Attacks occurring before puberty or after age 40 years are unusual unless a major provocation, such as new use of phenobarbital or estrogens, had occurred.