Attacks Of Acute Intermittent Porphyria Research Articles

Takotsubo syndrome triggered by acute intermittent porphyria attack: An unusual stressor for catecholamine-induced cardiomyopathy

a Pole d'activite medico-chirurgicale, Nouvel Hopital Civil, Hopitaux universitaires de Strasbourg, France b Pole Anesthesie-Reanimation Chirurgicale, SAMU, Nouvel Hopital Civil, Hopitaux universitaires de Strasbourg, France c Service de medecine interne, Nouvel Hopital Civil, Hopitaux universitaires de Strasbourg, France d Laboratoire EA 3072: «Mitochondries, stress oxydant et protection musculaire», Institut de Physiologie, Faculte de Medecine, Universite de Strasbourg, France

Acute Intermittent Porphyria

Edited by: Ya-Lin Bao Source of Support: Nil. Conflict of Interest: None declared.

Vitamin D-binding protein as a biomarker of active disease in acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by a deficiency of hepatic porphobilinogen deaminase (PBGD). The disease is characterized by life threatening acute neurovisceral attacks. The aim of this study was to identify metabolites secreted by the hepatocytes that reflect differential metabolic status in the liver and that may predict response to the acute attack treatment. Plasma vitamin D binding protein (VDBP) from a mouse model of AIP displayed an abnormal migration in 2D-electrophoresis that is efficiently recovered upon gene therapy leading to liver specific over-expression of the PBGD protein. The change in VDBP mobility results from a differential isoelectric point suggesting a post-translational modification that takes place preferably in the liver. Liquid chromatography–mass spectrometry (LC–MS) analysis of human samples before and after glycosidase treatment revealed glycosylated plasma VDBP specifically in patients with recurrent attacks of AIP. Glycosylated VDBP recovered normal values in three severely afflicted AIP patients submitted to therapeutic liver transplantation. Our findings suggest that post-translational modification of VDBP might be considered as a promising biomarker to study and monitor the liver metabolic status in patients with AIP. SignificanceWe describe an increased glycosylation of VDBP in porphyric livers. Normal glycosylation was recovered upon liver gene therapy in a mouse model of porphyria or after liver transplantation in severely afflicted patients with AIP. Moreover, quantification of glycosylated VDBP by our ELISA immunoassay or LC–MS protocol in patients undergoing PBGD-gene therapy (www.aipgene.org) may be used as a marker indicating improvement or normalization of the patient's hepatic metabolism.This article is part of a Special Issue entitled: HUPO 2014.

Preclinical Development of a Subcutaneous ALAS1 RNAi Therapeutic for Treatment of Hepatic Porphyrias Using Circulating RNA Quantification.

The acute hepatic porphyrias are caused by inherited enzymatic deficiencies in the heme biosynthesis pathway. Induction of the first enzyme 5-aminolevulinic acid synthase 1 (ALAS1) by triggers such as fasting or drug exposure can lead to accumulation of neurotoxic heme intermediates that cause disease symptoms. We have demonstrated that hepatic ALAS1 silencing using siRNA in a lipid nanoparticle effectively prevents and treats induced attacks in a mouse model of acute intermittent porphyria. Herein, we report the development of ALN-AS1, an investigational GalNAc-conjugated RNAi therapeutic targeting ALAS1. One challenge in advancing ALN-AS1 to patients is the inability to detect liver ALAS1 mRNA in the absence of liver biopsies. We here describe a less invasive circulating extracellular RNA detection assay to monitor RNAi drug activity in serum and urine. A striking correlation in ALAS1 mRNA was observed across liver, serum, and urine in both rodents and nonhuman primates (NHPs) following treatment with ALN-AS1. Moreover, in donor-matched human urine and serum, we demonstrate a notable correspondence in ALAS1 levels, minimal interday assay variability, low interpatient variability from serial sample collections, and the ability to distinguish between healthy volunteers and porphyria patients with induced ALAS1 levels. The collective data highlight the potential utility of this assay in the clinical development of ALN-AS1, and in broadening our understanding of acute hepatic porphyrias disease pathophysiology.

Urinary Metabolic Fingerprint of Acute Intermittent Porphyria Analyzed by 1H NMR Spectroscopy

(1)H NMR is a nonbiased technique for the quantification of small molecules that could result in the identification and characterization of potential biomarkers with prognostic value and contribute to better understand pathophysiology of diseases. In this study, we used (1)H NMR spectroscopy to analyze the urinary metabolome of patients with acute intermittent porphyria (AIP), an inherited metabolic disorder of heme biosynthesis in which an accumulation of the heme precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) promotes sudden neurovisceral attacks, which can be life-threatening. Our objectives were (1) to demonstrate the usefulness of (1)H NMR to identify and quantify ALA and PBG in urines from AIP patients and (2) to identify metabolites that would predict the response to AIP crisis treatment and reflect differential metabolic reprogramming. Our results indicate that (1)H NMR can help to diagnose AIP attacks based on the identification of ALA and PBG. We also show that glycin concentration increases in urines from patients with frequent recurrences at the end of the treatment, after an initial decrease, whereas PBG concentration remains low. Although the reasons for this altered are elusive, these findings indicate that a glycin metabolic reprogramming occurs in AIPr patients and is associated with recurrence. Our results validate the proof of concept of the usefulness of (1)H NMR spectroscopy in clinical chemistry for the diagnosis of acute attack of AIP and identify urinary glycin as a potential marker of recurrence of AIP acute attacks.

Urinary excretion of porphyrins, porphobilinogen and δ-aminolaevulinic acid following an attack of acute intermittent porphyria

Background and objectivesThe porphyrias are a group of rare, mainly inherited, diseases caused by a deficiency of one of the enzymes of the haem biosynthesis pathway. The biochemical hallmark of...

C4 A case of the great and little imitator

We present a case of Acute Intermittent Porphyria (AIP) exacerbated by HAART and review the complications of managing these two conditions. Only one previous case of these two conditions has been published. AB is a middle aged man who was diagnosed with HIV with baseline CD4 of 518. He was well until 2011 when he was admitted to our department with severe abdominal pain, hypotension and a penile ulcer. CT, MRCP, OGD and ultrasound were normal but syphilis serology was positive. He was treated with benzathine, his pain reduced and was discharged. He was then started on Atripla with a CD4 of 162. After 3 weeks he developed severe abdominal pain, hypertension and complained of ‘bloody’ urine but no blood on analysis. Biochemistry showed a sodium of 117. With these new symptoms urinary porphyrins were requested which were elevated at 4002 nmol/l representing an acute episode of AIP. It was felt this second admission was triggered by HAART which was stopped and he was treated with haem arginate and his symptoms improved. On further discussion with AB he admitted to taking a ‘legal high’ prior to the first admission which may have triggered this episode. There have been no reported cases of AIP due to syphilis. AIP is a disorder of the haem pathway and is known as the Little Imitator in contrast to syphilis the Great Imitator as it is often misdiagnosed. While it is a rare condition its importance with HIV is that it is triggered by most drugs needed in managing HIV. Drugs which induce cytochrome p450, anti PCP, TB and fungal agents have all been implicated. NRTI's are thought to be safe while Saquinavir is the only PI recommended for use and there is no evidence of newer HIV agents. AB was started on Truvada and boosted Saquinavir and 4 months on his symptoms are controlled with no further AIP attacks and viral load is 42 c/ml. Reports such as this are important in increasing the limited knowledge of safely co-treating HIV and AIP.Correction noticeThis article has been corrected since it was published. The text has had minor edits made to protect patient anonymity.

Acute intermittent porphyria

Introduction. Porphyria is the disease with insufficiency of some enzymes for heme synthesis and their precursors with the excessive accumulation of one or more porphyrins, porphyrinogens and/or porphyrin precursors. Clinical manifestations include unspecific systemic manifestation. Case presentation. We describe a 32 years old man who has been admitted at Center for Urgent medicine of Clinical Centre Kragujevac with abdominal pain, tachycardia and attack of epilepsy. The laboratory findings showed: normal blood cell accounts, positive humoral signs of inflammation, increased parameters of liver and muscle necrosis, electrolyte disturbances (hyponatremia), hypoproteinemia, normal lipid status and normal concentrations of parameters of renal function. Chest radiography indicated bronchopneumonia. Laboratory registered higher values of delta-aminolevulinic acid and porphobilinogen in urine. Conclusion. We reported the case of patient with acute intermittent porphyria. According to positive family history, clinical findings with positive specific markers in urine (increased ALA, PBG) we concluded that it was the first attack of acute intermittent porphyria. Porphyria is a very rare disease in clinical practice and it can present differential diagnostic problem in acute abdominal pain, often in emergency medicine.

Sustained Enzymatic Correction by rAAV-Mediated Liver Gene Therapy Protects Against Induced Motor Neuropathy in Acute Porphyria Mice

Acute intermittent porphyria (AIP) is characterized by a hereditary deficiency of hepatic porphobilinogen deaminase (PBGD) activity. Clinical features are acute neurovisceral attacks accompanied by overproduction of porphyrin precursors in the liver. Recurrent life-threatening attacks can be cured only by liver transplantation. We developed recombinant adeno-associated virus (rAAV) vectors expressing human PBGD protein driven by a liver-specific promoter to provide sustained protection against induced attacks in a predictive model for AIP. Phenobarbital injections in AIP mice induced porphyrin precursor accumulation, functional block of nerve conduction, and progressive loss of large-caliber axons in the sciatic nerve. Hepatocyte transduction showed no gender variation after rAAV2/8 injection, while rAAV2/5 showed lower transduction efficiency in females than males. Full protection against induced phenobarbital-attacks was achieved in animals showing over 10% of hepatocytes expressing high amounts of PBGD. More importantly, sustained hepatic expression of hPBGD protected against loss of large-caliber axons in the sciatic nerve and disturbances in nerve conduction velocity as induced by recurrent phenobarbital administrations. These data show for the first time that porphyrin precursors generated in the liver interfere with motor function. rAAV2/5-hPBGD vector can be produced in sufficient quantity for an intended gene therapy trial in patients with recurrent life-threatening porphyria attacks.

Screening for hepatocellular carcinoma in acute intermittent porphyria: a 15-year follow-up in northern Sweden

To evaluate the benefit of screening for hepatocellular carcinoma (HCC) in gene carriers of acute intermittent porphyria (AIP) and estimate the annual incidence of HCC in this group. All AIP gene carriers aged ≥55 years from the northernmost county in Sweden, Norrbotten, were invited for screening in this prospective study every 1-1.5 years during the period 1994-2009. We registered all HCC cases amongst AIP gene carriers in the northern region of Sweden (four counties). We compared gene carriers with repeated screening intervals of <2 years (Group A) with controls (Group B; i.e. gene carriers who had never been screened, those screened for the first time or screened at intervals of >2 years, or dropouts). The screening included radiological examination of the liver and relevant laboratory tests. A total of 62 AIP subjects participated in the study, comprising 33% of the total AIP population aged >55 years in the northern region of Sweden. HCC was diagnosed in 22 AIP subjects (12 men and 10 women), mean age 69 (59-82) years. Amongst these subjects, 73% had experienced prior AIP attacks. The incidence rate ratio for HCC was 64 (52 in men and 93 in women). There were no cases of hepatitis B/C or alcohol abuse. Liver cirrhosis was rare. Liver resection could be performed in most subjects in Group A. Fourteen patients died of HCC, one in Group A and 13 in Group B. Compared with those who were not screened regularly, screening was associated with improved 3-year and 5-year survival (P = 0.005 and 0.038). Screening for HCC in carriers of AIP enables early diagnosis and a choice of potentially curative treatments with improved prognosis. We recommend annual screening using liver imaging for AIP gene carriers >50 years of age.

Circulating fluorocytes at the first attack of acute intermittent porphyria: A missing link in the pathogenesis

Background Acute intermittent porphyria (AIP) is an autosomal dominant disorder of the haem biosynthesis resulting from a partial deficiency of hydroxymethylbilane synthase (HMBS) with incomplete penetrance. By conventional means, it is able to identify asymptomatic mutation carrier by molecular diagnosis, but one cannot reliably predict an acute porphyric attack. The presence of fluorescent red cells (fluorocytes) in AIP is probably under-recognized since AIP is a hepatic porphyria and not associated with photosensitivity. Methods We used an automatic image acquisition platform to detect the circulating fluorocytes at 700 nm emission in a diabetic AIP patient during acute attack. We screened the patient and her family members for the mutation on HMBS, urine porphobilinogen and circulating fluorocytes. Results The patient was heterozygous for a disease-causing mutation on HMBS and several bright circulating fluorocytes were detected. We showed evidence that protoporphyrin contributed to the erythrocyte auto-fluorescence. Interestingly, asymptomatic mutation carriers with increased urine porphobilinogen did not have circulating fluorocytes. All mutation-negative family members revealed no circulating fluorocytes. Conclusion Sudden decrease in plasma glucose concentration might invoke acute attack of AIP and appearance of circulatory fluorocytes. Potential of detecting fluorocytes as screening test or for predicting an acute attack of AIP in diabetes is worth investigating.

AAV8-mediated Gene Therapy Prevents Induced Biochemical Attacks of Acute Intermittent Porphyria and Improves Neuromotor Function

Acute intermittent porphyria (AIP), an autosomal dominant hepatic porphyria due to half-normal hydroxymethylbilane synthase (HMB-synthase) activity, is manifested by life-threatening acute neurological attacks that are precipitated by factors that induce heme biosynthesis. The acute attacks are currently treated with intravenous hemin, but a more continuous therapy is needed, particularly for patients experiencing frequent attacks. Thus, a recombinant AAV8-based serotype vector expressing murine HMB-synthase driven by liver-specific regulatory elements was generated and its effectiveness to prevent the biochemical induction of an acute attack was evaluated in an AIP mouse model. Intraperitoneal administration of the adeno-associated viral (AAV) vector resulted in a rapid and dose-dependent increase of HMB-synthase activity that was restricted to the liver. Stable expression of hepatic HMB-synthase was achieved and wild-type or greater levels were sustained for 36 weeks. When heme synthesis was periodically induced by a series of phenobarbital injections, the treated mice did not accumulate urinary delta-aminolevulinic acid (ALA) or porphobilinogen (PBG), indicating that the expressed enzyme was functional in vivo and prevented induction of the acute attack. Further, rotarod performance and footprint analyses improved significantly. Thus, liver-directed gene therapy provided successful long-term correction of the hepatic metabolic abnormalities and improved neuromotor function in the murine model of human AIP.

An unusual suicide attempt: a case with psychosis during an acute porphyric attack

The porphyrias are a heterogeneous group of disorders characterized by abnormal heme biosynthesis. Although all subtypes are rare, acute intermittent porphyria (AIP) is the most common form of the neuroporphyrias. Abdominal pain, peripheral neuropathy, and changes in cognitive function are the classical triad of an acute porphyric attack but the variability of the symptoms may interfere with the diagnosis of AIP. Delayed diagnosis and treatment of acute porphyric attacks, however, can be fatal or may cause long-term or permanent neurological damage. We hereby report a case of 45-year-old male with suicide attempt because of his psychotic symptoms during an AIP attack.

Clinical aspects of acute intermittent porphyria in northern Sweden: A population-based study

The objective of this study was to update the clinical issues of acute intermittent porphyria (AIP), as they have not been in focus for years, and to be aware of potentially associated disorders and social consequences. A total of 356 gene carriers of AIP from northern Sweden participated in this retrospective population-based study. Eight mutations were found with a predominance of W198X (89%). Clinical manifestations of AIP (manifest AIP) were identified in 42%, 65% were women. Women were more severely stricken by AIP attacks concerning number and duration, hospital admission and early onset. Men reporting most attacks were > 40 years of age. In addition to traditional symptoms during attacks, fatigue was commonly described. Chronic AIP symptoms and disability pension due to AIP were reported in about 20% of subjects. Precipitating factors were reported with evident sex differences. Half of the gene carriers who were on medications used drugs considered not safe (in 1999), mainly antihypertensive drugs. Smoking was associated with high AIP attack frequency. Elevated levels of ALT, bile acids, creatinine, U-ALA and U-PBG and decreased levels of creatinine clearance were associated with manifest AIP. The same was true for hypertension and myalgia in the legs. Hepatoma was strikingly overrepresented. The high prevalence of manifest AIP in this study could be explained by a mutation-dependent penetrance. Our results emphasize the importance of early diagnosis, counselling and treatment of attacks, screening and treatment of associated disorders.

Plasma porphobilinogen as a sensitive biomarker to monitor the clinical and therapeutic course of acute intermittent porphyria attacks

Background Acute intermittent porphyria (AIP) is a metabolic disease affecting hepatic heme biosynthesis. The clinical course in overt disease is characterized by acute attacks of neurovisceral symptoms. Treatment is based on symptomatic relief together with carbohydrate loading and in more severe attacks heme therapy. During an acute attack the heme precursors porphobilinogen (PBG) and 5-aminolevulinic acid (ALA) are produced in high amounts by the liver and are found in high concentrations in plasma and urine. These metabolites represent the acute phase reactants confirming an ongoing attack and are used to evaluate therapeutic measures. The aim of this study was to measure PBG and ALA in plasma and urine during an acute attack and to match the biochemical pattern with the clinical and therapeutical course. Methods Three consecutive AIP patients were included during four acute attacks. Plasma PBG and ALA were measured by a LC-MS method and in urine by ion-exchange chromatography. The patients received symptomatic and glucose treatment at admission to hospital, and four days later, if necessary, heme therapy. Results In the three attacks that required heme therapy, plasma PBG concentrations had further increased after admission ( p = 0.01). In the patient that did not require heme therapy, plasma PBG had decreased after admission. Conclusions Biochemical monitoring of an acute attack was more accurately reflected by plasma PBG than plasma ALA or urinary PBG and ALA. Glucose administration, in contrast to heme therapy, was not sufficient to achieve clinical and biochemical remission in the more serious attacks.

Hemodialysis: A therapeutic option for severe attacks of acute intermittent porphyria in developing countries

Acute intermittent prophyria (AIP) is an autosomal dominant disease that results from a defect in the enzyme porphobilinogen deaminase. Acute intermittent porphyria is the most common of hepatic porphyrias and can tax the therapeutic capabilities of the physician to the limit. Motor weakness is a major feature of an acute attack, and flaccid paralysis of all extremities can occur rapidly, within a matter of days. The acute attacks may be life threatening. Hematin (Heme Arginate) should be given early during an acute attack to prevent neurologic sequel. Hemodialysis and hemoperfusion have been tried in the treatment of acute attacks of AIP with success. As hematin is not available in India, a severe acute attack of AIP in a patient was managed with hemodialysis successfully. Later, hematin was imported and provided to the patient. An 18-year-old girl was admitted to our hospital with recurrent abdominal pain and 2 episodes of convulsions. She had undergone an appendectomy earlier at another hospital for abdominal pain. On evaluation, she had hyponatremia, episodic abnormal behavior, generalized muscle pain, hypertension, and sinus tachycardia. In view of the above clinical picture, a clinical diagnosis of acute intermittent porphyria was made. Her 24-hr urinary porphobilinogen was 90.8 mg/day (<2 mg-normal) and alpha amino levalunic acid was 108.8 mg/day (1-7 mg-normal), consistent with the diagnosis. Her hyponatremia was corrected. Arrangements were made to import hematin and she was managed with dextrose infusion. Meanwhile, she developed flaccid quardriparesis with urinary incontinence and bulbar palsy. Her brain MRI was normal. Her nerve conduction study was suggestive of motor radiculoneuropathy. Specific treatment for severe porphyric crisis was planned. She failed to improve with dextrose infusion alone. As hematin was not readily available in the country, other therapeutic options were considered. As few case reports of AIP being successfully treated with hemodialysis were available, the option of dialytic support was explained to the family. After procuring informed consent, she was subjected to hemodialysis for 4 hr in the first day, increasing to 6 hr a day for the next 6 days. Her abdominal pain and myalgia subsided on the third day of dialysis. Her lower limb muscle power improved and she became ambulant by the fourth day. Urinary retention improved within 4 days. Hematin was imported by then from the United States. Later, 2 doses of hematin (4 mg/kg-160 mg in 20% albumin) were given via a central vein. She was maintained on physiotherapy. Repeat nerve conduction study revealed recovery. She has been provided with a list of drugs that have to be avoided. Currently, she is on outpatient follow-up with occasional abdominal pain, which subsides with intravenous dextrose therapy.

Safety of amlodipine use in patients with acute intermittent porphyria

Acute intermittent porphyria (AIP) is probably the most common of the genetic porphyrias [1]. Drugs reported as unsafe in patients with porphyria include sulphonamides, erythromycin, barbiturates, hydantoins, carbamazepine, valproate, oestrogens, oral contraceptives, tricyclic antidepressants, benzodiazepines, calcium channel blockers [2] (especially nifedipine) and angiotensin-converting enzyme inhibitors (especially enalapril) [3]. We report here a case of AIP where the patient used amlodipine for hypertension and was free from attacks. A 28-year-old female patient who has been followed up with the diagnosis of AIP for 6 years was admitted to our outpatient clinic. The diagnosis had been made at our university clinic 6 years previously after finding 24-h urinary porphobilinogen excretion of 10.2 mg (normal values 0–2.0 mg) and 24 h urinary aminolaevulinic acid excretion of 7.2 mg (normal 0–7.0 mg), upon presentation to our emergency clinic with severe abdominal pain and mental status change. The patient had had 17 AIP attacks during 6 years of follow-up. The attacks ranged from severe abdominal pain to respiratory and following cardiac arrest. Attacks were provoked by the use of ‘unsafe drugs in acute porphyrias’, urinary tract infections and lower respiratory tract infections, which had been managed appropriately. She had been treated for hypertension for the last 2 years. Atenolol 100-mg tablets p.o. qd were started, but as arterial blood pressures approached 150/85 mmHg, the dose of atenolol had to be increased to 100-mg tablets p.o. bid a week later. Her hypertension remained well controlled until about 10 months later, when she started to have high blood pressure readings of approximately 160/90 mmHg. Amlodipine tablets 5 mg p.o. qd were added to the regimen, the dose increasing to 10 mg p.o. qd a few days later. Blood pressure control was achieved around 130/80 mmHg with this regimen. The patient remained on 100-mg atenolol tablets p.o. bid and amlodipine 10-mg tablets p.o. qd for the last 10 months with stable arterial blood pressure control at approximately 130/80 mmHg. The patient was closely followed up during last 10 months with regular office visits, during which detailed history and physical examination was performed. She remained AIP attack and symptom free during this period. Hypertension in subjects with AIP is due to sympathetic overactivity [4]. Hypertension and impaired renal function are commonly found in AIP, but most drugs for hypertension are contraindicated, either because they have precipitated attacks or because they are porphyrinogenic in nonhuman tissue [1]. Safe antihypertensive drugs are limited to β-adrenoceptor blockers, mainly propranolol, and the peripheral sympathetic neurone-blocking compounds guanethidine and bethadine [5]. Calcium channel blockers, especially nifedipine, are known to be unsafe. There are contradictory reports about amlodipine classifying the drug as safe [5] and unsafe [6]. Our report is another positive indicator for amlodipine use in AIP. When the prevalence and limited number of safe drugs for hypertension in AIP patients are taken into account, amlodipine may still be tried with caution in patients needing combination therapy.

Premenstrual Attacks of Acute Intermittent Porphyria in an Adolescent Female

Background: Acute intermittent porphyria (AIP) is an autosomal dominant inherited disorder causing decreased activity of the heme biosynthetic pathway. AIP can be a severe and potentially life-threatening syndrome which presents a clinical quandary. Endogenous steroids are significant determinants of disease activity, as displayed by the female preponderance, the rarity of attacks prior to puberty and after middle age, and the presentation of premenstrual attacks in women. Patients with AIP require prompt evaluation, diagnosis, and management.

Premenstrual Attacks of Acute Intermittent Porphyria in an Adolescent Female

Premenstrual Attacks of Acute Intermittent Porphyria in an Adolescent Female

Estimation and Application of Biological Variation of Urinary δ-Aminolevulinic Acid and Porphobilinogen in Healthy Individuals and in Patients with Acute Intermittent Porphyria

Diagnosis of an attack of acute intermittent porphyria (AIP) is based on the demonstration of increased concentrations of porphobilinogen (PBG) and delta-aminolevulinic acid (ALA) in urine, but many AIP patients also have high baseline concentrations in remission. The aim of this study was to estimate the biological variations of ALA, PBG, and porphyrins in healthy individuals and AIP patients to improve interpretation of test results. Fifteen healthy individuals and 15 AIP patients were included, and biological variations were calculated based on urine samples collected weekly for 10 consecutive weeks. For the AIP patients, long-term variations were also estimated based on 7 samples collected through a 2-year period. The porphyrin variances were inhomogeneously distributed; biological variations of porphyrins were therefore not calculated. The within-subject biological variations of ALA and PBG were 16%-20% in the short-term settings and for PBG, 25% in the long-term setting, giving reference change values of approximately 50% and 70%, respectively. The probability of detecting a 100% real change in PBG was 97% in the short-term setting and 80% in the long-term setting. In an AIP patient, a 2-fold increase in PBG, independent of the baseline concentration, will be detected with a probability >80% and is most likely related to the patient's disease and not caused only by analytical and biological variation. When PBG is used in the assessment of AIP-related symptoms, both the PBG concentration in remission and the length of time since the previous sample must be considered.