Increased activity of porphobilinogen deaminase in erythrocytes during attacks of acute intermittent porphyria

The activity of porphobilinogen deaminase was determined in 25 patients with acute intermittent porphyria during and after fully developed attacks of porphyria. It was found that in most cases (in 20 of 25) it was higher than 24.3 nmoles/ml erythrocytes/hour, a value considered as characteristic for acute intermittent porphyria, and that it decreased during convalescence and remission. In a proportion of these cases the decrease in the activity of the enzyme was parallelled by decreasing urinary excretion of porphobilinogen. A normal activity of porphobilinogen deaminase during an attack of porphyria can be a source of error in the differential diagnosis of porphyria.     

Changes of myocardial functions in acute hepatic porphyrias. Role of heme arginate administration

In three patients with attacks of acute intermittent porphyria we found markedly impaired functions of the left ventricle accompanied by ECG changes that returned to normal after administration of heme arginate or cytochrome C administration. In nine patients with other types of porphyria, and in one patient with acute intermittent porphyria not suffering an attack, no significant changes of left ventricle function were observed. The changes seen in patients with an acute attack may be ascribed to acute myocardial hypoxia resulting from defective biosynthesis of heme. We assume that the exogenous supply of heme may improve cellular hypoxia.     

Psychotropic drugs in acute intermittent porphyria.

Acute intermittent porphyria is one of a group of metabolic diseases called the porphyrias that may lead to symptoms of the central nervous system during an acute exacerbation. Certain drugs such as barbiturates are known to precipitate attacks of acute intermittent porphyria, but unfortunately there is little information regarding the safety of many psychotropic drugs in this disorder, especially the newer antidepressants and atypical antipsychotics. We report a case of an elderly patient with acute intermittent porphyria who was treated with a variety of psychotropic agents for a severe depression with psychotic features. Although many of the agents did not improve the psychiatric status of the patient, all the drugs were tolerated without precipitating an episode of acute intermittent porphyria. To our knowledge, this is the first report of the safe use of sertraline, venlafaxine, olanzapine, risperidone, clozapine, buspirone, trazodone, lorazepam, and clonazepam in a patient with documented acute intermittent porphyria. Our report also supports the safety of trifluoperazine. Although response and sensitivity to drugs may vary greatly among patients with this disorder, clinicians may want to consider the possibility of the above drugs to treat psychiatric symptoms in patients with acute intermittent porphyria.     

Denaturing gradient gel electrophoresis for rapid detection of latent carriers of a subtype of acute intermittent porphyria with normal erythrocyte porphobilinogen deaminase activity.

Acute intermittent porphyria is an autosomal dominant disorder defined by a partial deficiency of porphobilinogen deaminase (EC 4.3.1.8). Clinical manifestations of the disease are characterized by acute attacks of neurological dysfunction often linked to environmental factors. Early diagnosis of gene carriers is important in the prevention of attacks and is usually achieved by determining the porphobilinogen deaminase activity in erythrocytes. However, in a subtype of acute intermittent porphyria, the enzymatic defect is restricted to nonerythropoietic cells. Different mutations have already been described that account for this phenotype in two unrelated families. We previously detected asymptomatic carriers by using mutation-specific probes after in vitro amplification of the target DNA sequence. In this study, we investigated the DNA of eight unrelated subjects with the same subtype of acute intermittent porphyria by using the polymerase chain reaction, with subsequent analysis of the amplified products by denaturing gradient gel electrophoresis. Five of these patients shared the same single-base change. This technique was quite simple and efficient for detecting asymptomatic carriers. Importantly, it is potentially useful for studying families with the same phenotypic subtype of the disease and possibly different mutations in the same DNA region.     

Hepatic porphyrias. Current concepts.

Acute intermittent porphyria, variegate porphyria, and hereditary coproporphyria are hepatic porphyrias due to enzyme defects that are inherited as autosomal dominants. Porphyria cutanea tarda is considered an acquired disorder. Similar drugs or circumstances are precipitants of acute attacks in all three inherited hepatic porphyrias. The respective biochemical abnormalities are identifiable by simple, readily available laboratory tests. Management of patients with any of the inherited hepatic porphyrias is directed primarily toward prevention of attacks through avoidance of precipitants and through a diet high in carbohydrate. Therapy for porphyria cutanea tarda includes interdiction of alcohol use and repeated phlebotomy.     

Elevation of hormone-binding globulins in acute intermittent porphyria

Sex hormone-binding globulin (SHBG), thyroxine-binding globulin (TBG) and cortisol-binding globulin (CBG) were measured in plasma of 26 patients with acute intermittent porphyria (AIP). Twelve patients had clinically manifest disease and all had elevated SHBG levels. All but one of 14 patients with latent porphyria had normal SHBG levels. TBG was elevated in 9 of the patients with clinically manifest porphyria and CBG elevated in three. Levels of TBG and CBG were either normal or only slightly elevated in those with latent porphyria. In a prospective study of 30 attacks of AIP in 7 patients, SHBG levels fell between admission and discharge, the fall being significant in the group of 21 attacks treated with haem arginate (p less than 0.001). Our findings suggest that a close correlation exists between elevated SHBG and clinical expression of AIP.     

Treatment with Haematin in Acute Hepatic Porphyria

We report our experience with intravenous haematin in the treatmentof 13 attacks of acute porphyria In eight patients. Seven patientshad acute intermittent porphyria and one variegate porphyria.Peripheral neuropathy was a feature of nine of the attacks andin two the neuropathy necessitated assisted ventilation. Thehaematin lowered the urinary excretion of porphyrins and precursorsin all patients by approximately 50 per cent of the pre-haematinvalues. It also repressed the activity of delta-aminolaevulinicacid synthase, the rate-controlling enzyme of haem biosynthesis,in peripheral leucocytes in seven of the nine patients in whomit was monitored. The clinical response was less consistent,with clinical Improvement accompanying only half of the courses.The two patients with respiratory paralysis died. There waslocalized phlebitis at the injection site following five ofthe courses but no other side-effects were noted. Previously published reports of haematin therapy for acute porphyriaare reviewed. These consist of 45 courses in 32 patients. Biochemicalimprovement was a consistent finding. Clinical response hasbeen less consistent Twenty-four of the courses were associatedwith sustained improvement, ten with temporary improvement—relapseoccurring within two to 14 days (three fatal). In eleven therewas no improvement and three died.     

Uroporphyrinogen synthase in erythrocytes in acute intermittent porphyria: new pathobiochemical aspects (author's transl)

Uroporphyrinogen synthase (EC 4.3.1.8) was determined in the erythrocytes of 380 patients, of which 21 showed clinical symptoms of acute intermittent porphyria. The normal range of a random sample was 61 +/- 23 mumol/1.h(x +/- 2s, n=302), including the activity of uroporphyrinogen cosynthase and the subsequent enzymes; when all the latter enzymes were destroyed by heating the haemolysate, the normal range for uroporphyrinogen synthase was 65 +/- 25 mumol/1.h(x +/- 2s, n=274). The respective activity of uroporphyrinogen synthase in patients with acute intermittent porphyria was 35 +/- 12, and 40 +/- 18 mumol/1.h which was significantly lower (p less than 0.001) than the control values. In the 21 cases of acute intermittent porphyria, the diagnosis had already been made from the presence of porphyrin precursors and porphyrin in the urine. In 7 of the 21 cases of acute intermittent porphyria, and in 6 relatives of the patients, the activity of the uroporphyrinogen synthase was in the overlap zone (40-50 mumol/1.h). 32 relatives of 9 of the patients with acute intermittent porphyria were investigated: 22 showed a significant decrease of uroporphyrinogen synthase, and 7 of these showed pathological urinary porphyrin precursors and porphyrin. The relative activity of uroporphyrinogen synthase in patients with acute intermittent porphyria was 57%. A decrease of the uroporphyrinogen synthase activity of greater than 30% compared with the mean of the controls is a sure indicator for the presence of a primary enzymic defect in the gene carrier for acute intermittent porphyria.     

Variant of acute intermittent porphyria with normal erythrocyte uroporphyrinogen-I-synthase activity

A kindred in which several members have otherwise typical acute intermittent porphyria but normal erythrocyte uroporphyrinogen-I-synthase activity has been described from Finland. We studied two porphyric members of this kindred, two patients with typical acute intermittent porphyria, and two healthy controls using the delta-aminolaevulinic acid loading test and by measuring the erythrocyte enzymes of haem biosynthesis. The excretion pattern of haem precursors after the delta-aminolaevulinic loading test in the members of the kindred studied, was similar to that in typical acute intermittent porphyria suggesting an identical enzyme defect in the liver. The activity of all red cell enzymes studied was normal in the members of the kindred. The results suggest that porphyria in the kindred studied is a variant of acute intermittent porphyria, where the uroporphyrinogen-I-synthase defect is manifested in the liver but not in red cells.     

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 δ-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.     

LHRH analogue treatment for the prevention of premenstrual attacks of acute porphyria

We have assessed the value of suppressing ovulation with the luteinizing hormone releasing hormone (LHRH) analogue buserelin in seven patients experiencing crises of acute intermittent porphyria related to the menstrual cycle. Clinical course, plasma oestradiol and progesterone levels, and urinary porphyrin and precursor excretion were monitored over a baseline period of approximately one year, and then for a similar period on buserelin treatment. There was a trend towards clinical improvement on buserelin therapy. The median number of attacks fell from seven during the baseline period to three on treatment (p = 0.06). The response to buserelin varied considerably, with those patients in whom the association between baseline attacks and the menstrual cycle was strongest gaining the most benefit. All patients became amenorrhoeic with suppression of plasma oestradiol and progesterone levels. Urinary delta-aminolaevulinic acid and total porphyrin excretion fluctuated widely both before and during treatment. Our experience indicates that ovulation suppression may be of value in the management of young women in whom recurrent attacks of porphyria are related to the menstrual cycle.     

Acute intermittent porphyria: biochemical and clinical analysis in the Argentinean population.

Acute intermittent porphyria (AIP) is the most common type of hepatic acute porphyria. In this work, we have analyzed the biochemical data of all Argentinean AIP families studied in the Porphyrins and Porphyrias Research Centre (CIPYP). We have shown that: (i) the prevalence for this population is about 1:125,000; (ii) the disease is more frequent in women than in men (7:3); (iii) about 60% are latent carriers; (iv) 15% of patients with symptomatic AIP died during an acute attack; (v) the most important precipitating factors of acute attacks in our population were the ingestion of therapeutic drugs (25%), anesthetics in surgical interventions (25%) and infections (20%); (vi) the initial symptom in Argentinean AIP individuals is severe abdominal pain (100%), and it is often accompanied by constipation (37%), anorexia (37%) and tachycardia (30%); and (vii) the percentage of recurrence of the acute attacks is high (81%).     

Clinical usefulness of cimetidine for the treatment of acute intermittent porphyria--a preliminary report

A 43-yr-old man with abdominal fullness was treated with oral cimetidine during remission of acute intermittent porphyria. Urinary prophobilinogen and porphyrins were not altered by the treatment, but urinary delta-aminolevulinic acid decreased, and abdominal fullness disappeared. Thus, cimetidine may control acute intermittent porphyria by inhibiting hepatic delta-aminolevulinic acid synthetase.     

Pneumonia

Abstract

The porphyrias are a group of metabolic diseases caused by inherited or acquired enzymatic deficiency in the metabolic pathway of heme biosynthesis. Simplistically, they can be considered as storage diseases, because the partial enzymatic defect gives rise to a metabolic “bottleneck” in the biosynthetic pathway and hence to an accumulation of different metabolic intermediates, potentially toxic and responsible for the various (cutaneous or neurovisceral) clinical manifestations observed in these diseases. In the acute porphyrias (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and the very rare delta-aminolevulinic acid dehydratase ALAD-d porphyria), the characteristic severe neurovisceral involvement is mainly ascribed to a tissue accumulation of delta-aminolevulinic acid, a neurotoxic nonporphyrin precursor. Many different factors, both endogenous and exogenous, may favor the accumulation of this precursor in patients who are carriers of an enzymatic defect consistent with an acute porphyria, thus contributing to trigger the serious (and potentially fatal) clinical manifestations of the disease (acute porphyric attacks). To date, many different drugs are known to be able to precipitate an acute porphyric attack, so that the acute porphyrias are also considered as pharmacogenetic or toxygenetic diseases. This article reviews the different biochemical mechanisms underlying the capacity of many drugs to precipitate a porphyric acute attack (drug porphyrogenicity) in carriers of genetic mutations responsible for acute porphyrias, and addresses the issue of prescribing drugs for patients affected by these rare, but extremely complex, diseases.     

Normeperidine-induced seizures in hereditary coproporphyria

Seizures are common in acute exacerbations of hepatic porphyria, even though the etiology is not identified in most cases. We have reported a case of normeperidine-induced seizures in a patient with hereditary coproporphyria. Although meperidine is commonly used for pain control during acute attacks in these patients, this report suggests that meperidine is not a good analgesic choice in porphyria. Normeperidine-induced seizures in patients with porphyria may be treated by withdrawal of meperidine therapy and selective use of anticonvulsants.     

The differentiation of the porphyrias by means of high pressure liquid chromatography

The analysis of faecal and urinary porphyrins by high pressure liquid chromatography (H.P.L.C.) provides characteristic profiles and facilitates rapid diagnosis of variegate (porphyria cutanea tarda hereditaria), symptomatic porphyria (porphyria cutanea tarda symptomatica), hereditary coproporphyria, acute intermittent porphyria, erythro-hepatic protoporphyria and congenital porphyria (erythropoietic porphyria).     

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.     

Induction of a deficiency of steroid delta 4-5 alpha-reductase activity in liver by a porphyrinogenic drug.

The hepatic enzymes that catalyze drug oxidations and the reductive metabolism of steroid hormones to 5alpha-derivatives are localized in membranes of the endoplasmic reticulum. Phenobarbital, which exacerbates acute intermittent porphyria in man, induces drug-oxidizing enzymes in liver. Additionally, patients in whome the primary gene defect (uroporphyrinogen-I-synthetase deficiency) of acute intermittent porphyria has become clinically expressed have low levels of hepatic steroid delta4-5alpha-reductase activity. This 5alpha-reductase deficiency in acute intermittent porphyria leads to the disproportionate generation of 5beta-steroid metabolites from precursor hormones; such steroid metabolites have significant porphyria-inducing action experimentally. In this study the effects of phenobarbital on drug oxidation and steroid 5alpha-reduction in man were examined to determine if this drug could produce changes in steroid 5alpha-reductase activity which mimicked those seen in patients with acute intermittent porphyria. Metabolic studies with [14C]-testosterone and 11beta-[3H]hydroxyandrostenedione were carried out in five normal volunteers. In all five subjects phenobarbital administration (2 mg/kg/per day for 21 days) enhanced plasma removal of the test drugs antipyrine and phenylbutazone as expected; but in four subjects phenobarbital also substantially depressed 5alpha-metabolite formation from [14C]testosterone and resulted in a pattern of hormone biotransformation characterized by a high ratio of 5beta/5alpha-metabolite formation. Studies with 11beta-[3H]hydroxy-androstenedione in three subjects confirmed that phenobarbital produced this high 5beta/5alpha ratio of steroid metabolism by depressing 5alpha-reductase activity for steroid hormones in liver. The high ratio of 5beta/5alpha-metabolites formed in normals after drug treatment mimicks the high 5beta/5alpha-steroid metabolite ratio formed from endogenous hormones in acute intermittent porphyria. The proximate mechanism by which phenobarbital induces reciprocal changes in activities of the microsomal enzymes which catalyze drug oxidations and steroid 5alpha-reductions is not known. This action of phenobarbital raises the possibility, however, that certain drugs which provoke exacerbations of human porphyria may do so, in part, by producing deleterious shifts in the patterns of endogenous steroid hormone metabolism.     

New form of dual porphyria: coexistent acute intermittent porphyria and porphyria cutanea tarda

A previously unrecognized form of dual porphyria has been identified in four patients. One male and one female with acute symptoms were diagnosed as having acute intermittent porphyria (AIP), and two males with cutaneous and acute symptoms were diagnosed as having porphyria cutanea tarda (PCT). Biochemically, the excretion of haem precursors showed a complex constellation, with signs characteristic of both AIP and PCT. In one male, a clinical course with both overt PCT and acute manifestations of AIP was observed. Enzyme studies of haem biosynthesis in erythrocytes revealed a dual deficiency, with decreased activity of both porphobilinogen deaminase, as seen in AIP, and uroporphyrinogen decarboxylase, as seen in PCT. A family study showed that the two disorders do not consistently segregate together. These findings suggest that the dual porphyria reflects a double heterozygous condition of coexistent AIP and PCT genes in the same subject.     

Endosonography-guided celiac plexus neurolysis in the treatment of pain secondary to acute intermittent porphyria

Acute intermittent porphyria is a metabolic error transmitted as an autosomal dominant disorder with incomplete penetrance. Its clinical picture includes intermittent abdominal pain, nausea, vomiting, and diarrhea, with or without neurological changes. We report the case of a young woman whose pain attacks were controlled with high-dose opiates, in whom we decided to perform endosonography-guided celiac plexus neurolysis (EUS-CPN). This is the first reported attempt with this new treatment option. There was significant clinical and nutritional improvement after treatment.