Clinical, Biochemical and Molecular Characteristics of the Main Types of Porphyria

Obstacles to Early Diagnosis of Acute Hepatic Porphyria: Current Perspectives on Improving Early Diagnosis and Clinical Management

Porphyrias are, for the most part, inherited disorders of the heme biosynthetic pathway which lead to accumulation of specific intermediates responsible for most of the symptoms and signs of biochemically active disease. Acute hepatic porphyrias usually come to clinical attention primarily in women in their reproductive years who present with episodic, severe, generalized abdominal pain. Such acute attacks may also be associated with tachycardia, systemic arterial hypertension, hyponatremia, recent history of dark reddish to brownish urine, and anxiety, delirium, and sensory or motor neuropathies. Diagnosing AHPs is often challenging, requiring a high index of suspicion and the appropriate testing showing elevated ALA and/or PBG in a random urine specimen. Obstacles to diagnosis include inappropriate testing for porphyrins only, inadequate sample handling, and ordering genetic testing as the initial diagnostic test. While some of these pitfalls in diagnosis are surmountable with current knowledge, others are in need of more research.

Intrahepatic Cholangiocarcinoma and Acute Intermittent Porphyria: A Case Report

Patients suffering from different forms of acute hepatic porphyria present a high risk of primary liver cancer, specifically hepatocellular carcinoma and cholangiocarcinoma, determined by the activity of the disease even though an exact mechanism of carcinogenesis has not been recognized yet. Here, we present the clinical case of a 72-year-old woman who, approximately 29 years after the diagnosis of acute intermittent porphyria, presented with intrahepatic cholangiocarcinoma with a histological diagnosis of adenocarcinoma starting from the biliary-pancreatic ducts, which was diagnosed during the clinical and anatomopathological evaluation of a pathological fracture of the femur.

Systematic review of the prevalence and incidence of the photodermatoses with meta-analysis of the prevalence of polymorphic light eruption

Information about the prevalence of photodermatoses is lacking, despite their substantial impact on life quality. Our objective was to systematically review the literature to establish what is known regarding prevalence and incidence of photodermatoses. We searched Medline, CINAHL and Embase from inception to 2021 to identify original population-based studies in English literature reporting the prevalence and/or incidence of photodermatoses. Information was extracted according to geographical location and risk of bias was assessed using a 10-point risk of bias tool for prevalence studies. Primary outcome was the population prevalence of photodermatoses. Prevalence data for polymorphic light eruption (PLE) were used to calculate the global pooled prevalence of PLE. Twenty-six studies were included; 15 reported prevalence of photodermatoses based on samples of the general population and 11 on prevalence and/or incidence from national and international registry data. The general population studies involved PLE (nine studies), unspecified photosensitivity (2), actinic prurigo (2), juvenile spring eruption (1), chronic actinic dermatitis (1) and variegate porphyria (1), while registry studies reported on cutaneous porphyrias and genophotodermatoses (nine and two studies, respectively). Worldwide the prevalence of PLE between countries ranged from 0.65% (China) to 21.4% (Ireland). The pooled estimated prevalence of PLE was 10% (95% CI 6%-15%) among the general population (n = 19,287), and PLE prevalence increased with distance from the equator (r = 0.78, p < 0.001). While several photodermatoses are rare, photosensitivity can be prevalent at wide-ranging world locations, including Egypt where photosensitivity was found in 4% of children and 10% of adults. This study showed that PLE is highly prevalent in many populations and that its prevalence shows a highly significant correlation with increasing northerly or southerly latitude. Available population-based studies for photodermatoses suggest they can be prevalent at a range of world locations; more attention is required to this area.

Circadian Genes Expression Patterns in Disorders Due to Enzyme Deficiencies in the Heme Biosynthetic Pathway

Heme is a member of the porphyrins family of cyclic tetrapyrroles and influences various cell processes and signalling pathways. Enzyme deficiencies in the heme biosynthetic pathway provoke rare human inherited metabolic diseases called porphyrias. Protein levels and activity of enzymes involved in the heme biosynthetic pathway and especially 5'-Aminolevulinate Synthase 1 are featured by 24-h rhythmic oscillations driven by the biological clock. Heme biosynthesis and circadian pathways intermingle with mutual modulatory roles. Notably, heme is a ligand of important cogs of the molecular clockwork, which upon heme binding recruit co-repressors and inhibit the transcription of numerous genes enriching metabolic pathways and encoding functional proteins bringing on crucial cell processes. Herein, we assessed mRNA levels of circadian genes in patients suffering from porphyrias and found several modifications of core clock genes and clock-controlled genes expression, associated with metabolic and electrolytic changes. Overall, our results show an altered expression of circadian genes accompanying heme biosynthesis disorders and confirm the need to deepen the knowledge of the mechanisms through which the alteration of the circadian clock circuitry could take part in determining signs and symptoms of porphyria patients and then again could represent a target for innovative therapeutic strategies.

Development and validation of diagnostic algorithms for the laboratory diagnosis of porphyrias

Porphyrias are rare metabolic disorders of the haem synthesis. They can present with acute neurovisceral attacks, cutaneous symptoms, or a combination of both. As they present with a wide variety of clinical symptoms, diagnosis is often delayed and correct interpretation of porphyria-related tests remains a challenge for many physicians. We developed and validated two algorithms for the laboratory diagnosis of porphyrias based on presenting symptoms. Based on a literature search and clinical/laboratory expertise, we developed algorithms for acute and cutaneous porphyrias. We validated these algorithms using all porphyria related laboratory test requests between January 1st 2000 and September 30th 2020 in UZ Leuven. In addition, we also evaluated our algorithm using samples from the European porphyria network (EPNET) external quality assessment scheme (2010-2021). Sensitivity of the algorithm for acute porphyria was 100.0% [74.9%-100.0%] (13 acute intermittent porphyria (AIP) and 1 variegate porphyria [VP]) with a specificity of 98.5% [91.0%-100.0%] (65 patients). Sensitivity of the algorithm for cutaneous porphyria was 100% [95.1%-100.0%] (7 VP, 59 porphyria cutanea tarda (PCT), 23 erythropoietic protoporphyria (EPP), 2 X-linked erythropoietic protoporphyria [XLEPP]) with a specificity of 93.9% [82.9%-98.5%]. There were no diagnostic samples of other types of porphyria. The algorithms correctly identified 18 of the 19 EPNET porphyria cases. One of the two hereditary coproporphyria cases was missed. The algorithms for acute and cutaneous porphyria showed high sensitivity and specificity and can be used to aid the clinician in correctly interpreting the laboratory findings of porphyria-related tests.

A 9-year-old girl with blisters on the hands and face: An early presentation of variegate porphyria

Variegate porphyria (VP) is a rare subtype of porphyrias characterized by dysfunction of enzymes in the heme biosynthesis pathway leading to an accumulation of porphyrins and their precursors. The resulting buildup can manifest as neuropsychiatric symptoms and photosensitive blistering eruptions on sun-exposed skin. We report a case of VP in a 9-year-old girl with many confounding medical factors that warranted alternative explanations for her cutaneous lesions. VP has been reported infrequently in the pediatric population and is associated with more severe neuropsychiatric outcomes compared to adult-onset disease.

Iron Metabolism in the Disorders of Heme Biosynthesis

Given its remarkable property to easily switch between different oxidative states, iron is essential in countless cellular functions which involve redox reactions. At the same time, uncontrolled interactions between iron and its surrounding milieu may be damaging to cells and tissues. Heme—the iron-chelated form of protoporphyrin IX—is a macrocyclic tetrapyrrole and a coordination complex for diatomic gases, accurately engineered by evolution to exploit the catalytic, oxygen-binding, and oxidoreductive properties of iron while minimizing its damaging effects on tissues. The majority of the body production of heme is ultimately incorporated into hemoglobin within mature erythrocytes; thus, regulation of heme biosynthesis by iron is central in erythropoiesis. Additionally, heme is a cofactor in several metabolic pathways, which can be modulated by iron-dependent signals as well. Impairment in some steps of the pathway of heme biosynthesis is the main pathogenetic mechanism of two groups of diseases collectively known as porphyrias and congenital sideroblastic anemias. In porphyrias, according to the specific enzyme involved, heme precursors accumulate up to the enzyme stop in disease-specific patterns and organs. Therefore, different porphyrias manifest themselves under strikingly different clinical pictures. In congenital sideroblastic anemias, instead, an altered utilization of mitochondrial iron by erythroid precursors leads to mitochondrial iron overload and an accumulation of ring sideroblasts in the bone marrow. In line with the complexity of the processes involved, the role of iron in these conditions is then multifarious. This review aims to summarise the most important lines of evidence concerning the interplay between iron and heme metabolism, as well as the clinical and experimental aspects of the role of iron in inherited conditions of altered heme biosynthesis.

Neurological Manifestations of Acute Porphyrias

PURPOSE OF REVIEW

Porphyrias constitute a group of rare metabolic disorders that result in a deficiency of the heme biosynthetic pathway and lead to the accumulation of metabolic intermediaries. Patients with porphyria can experience recurrent neurovisceral attacks which are characterized by neuropathic abdominal pain and acute gastrointestinal symptoms, including nausea, vomiting, and constipation. Depending on the type of porphyria, patients can present with cutaneous manifestations, such as severe skin photosensitivity, chronic hemolysis, or evidence of neurologic dysfunction, including alterations in consciousness, neurovascular involvement, seizures, transient sensor-motor symptoms, polyneuropathy, and behavioral abnormalities.

RECENT FINDINGS

More recently, cases of posterior reversible encephalopathy syndrome, cerebral vasoconstriction, and acute flaccid paralysis have also been described. While the exact pathogenic mechanisms linking the accumulation of abnormal heme biosynthetic intermediaries to neurologic manifestations have not been completely elucidated, it has been proposed that these manifestations are more common than previously thought and can result in permanent neurologic injury. This article reviews the basic principles of heme synthesis as well as the pathogenic mechanism of disease, presentation, and treatment of acute hepatic porphyrias with emphasis on those with neurologic manifestations.

RNAi therapy with givosiran significantly reduces attack rates in acute intermittent porphyria

Acute hepatic porphyria (AHP) is a group of inherited metabolic disorders that affect hepatic heme biosynthesis. They are associated with attacks of neurovisceral manifestations that can be life threatening and constitute what is considered an acute porphyria attack. Until recently, the sole specific treatment for acute porphyria attacks consisted of the intravenous administration of hemin. Although attacks are often sporadic, some patients develop recurrent acute attacks, with devastating effects on quality of life. Liver transplantation has historically been the sole curative treatment option. The clinical manifestations of AHP are attributed to the accumulation of the heme precursor 5-aminolevulinic acid (ALA) and porphobilinogen (PBG). Advances in molecular engineering have provided new therapeutic possibilities for modifying the heme synthetic pathway. We reviewed the background and current status of AHP treatment using liver-directed small interfering RNA targeting ALAS1. The therapeutic aim was to normalize the levels of ALAS1, which is highly upregulated during acute porphyria attacks. Givosiran is now an approved drug for use in adults and adolescents aged 12 years and older. The results of clinical trials have shown that givosiran treatment leads to a rapid and sustained reduction of ALAS1 mRNA, decreased heme precursor levels, and a decreased rate of acute attacks compared with placebo. The clinical trials (phases I, II, and III) were all randomized and placebo controlled. Many patients enrolled in the initial clinical trials have continued treatment in open label extension and extended/compassionate-use programs in countries where givosiran is not yet commercially available.

Cutting-Edge Therapies and Novel Strategies for Acute Intermittent Porphyria: Step-by-Step towards the Solution

Acute intermittent porphyria (AIP) is an autosomal dominant disease caused by the hepatic deficiency of porphobilinogen deaminase (PBGD) and the slowdown of heme biosynthesis. AIP symptomatology includes life-threatening, acute neurovisceral or neuropsychiatric attacks manifesting in response to precipitating factors. The latter promote the upregulation of 5-aminolevulinic acid synthase-1 (ALAS1), the first enzyme of heme biosynthesis, which promotes the overload of neurotoxic porphyrin precursors. Hemin or glucose infusions are the first-line therapies for the reduction of ALAS1 levels in patients with mild to severe AIP, while liver transplantation is the only curative treatment for refractory patients. Recently, the RNA-interference against ALAS1 was approved as a treatment for adult and adolescent patients with AIP. These emerging therapies aim to substitute dysfunctional PBGD with adeno-associated vectors for genome editing, human PBGD mRNA encapsulated in lipid nanoparticles, or PBGD protein linked to apolipoprotein A1. Finally, the impairment of glucose metabolism linked to insulin resistance, and mitochondrial aberrations during AIP pathophysiology provided new therapeutic targets. Therefore, the use of liver-targeted insulin and insulin-mimetics such as α-lipoic acid may be useful for overcoming metabolic dysfunction in these subjects. Herein, the present review aims to provide an overview of AIP pathophysiology and management, focusing on conventional and recent therapeutical approaches.

Diagnosis of acute intermittent porphyria in a renal transplant patient: A case report

BACKGROUND

Acute intermittent porphyria (AIP) is an inherited disorder of porphyrin metabolism with a worldwide distribution and a prevalence ranging from 1 to 9 per million population. AIP is caused by an autosomal dominant-inherited mutation of low penetrance resulting in a deficiency of porphobilinogen deaminase (PBGD) activity. Acute attacks are provoked by stressors such as certain medications, alcohol, and infection. We herein present the first case report of AIP detected in a post-renal transplant patient.

CASE SUMMARY

The patient was a 65-year-old man who underwent transplantation 2 years previously for suspected nephroangiosclerosis and chronic interstitial nephro-pathy. He subsequently developed diabetes mellitus which required insulin therapy. He had been treated in the recent past with local mesalamine for proctitis. He presented with classic but common symptoms of AIP including intense abdominal pain, hypertension, and anxiety. He had multiple visits to the emergency room over a 6-mo period for these same symptoms before the diagnosis of AIP was entertained. His urinary postprandial blood glucose level was 60 mg/24 h (normal, < 2 mg/24 h). He was placed on a high carbohydrate diet, and his symptoms slowly improved.

CONCLUSION

This case report describes a common presentation of an uncommon disease, in which post-transplant complications and medications may have contributed to precipitating the previously undiagnosed AIP. We hypothesize that the low-carbohydrate diet and insulin with which our patient was treated may have led to the attacks of AIP. Alternatively, our patient's mesalamine treatment for proctitis may have led to an acute AIP crisis. A high index of suspicion is needed to consider the diagnosis of a heme synthesis disorder, which presents with the common symptoms of abdominal pain, high blood pressure, and anxiety.

Kidney Involvement in Acute Hepatic Porphyrias: Pathophysiology and Diagnostic Implications

Porphyrias are a group of rare disorders originating from an enzyme dysfunction in the pathway of heme biosynthesis. Depending on the specific enzyme involved, porphyrias manifest under drastically different clinical pictures. The most dramatic presentation of the four congenital acute hepatic porphyrias (AHPs: acute intermittent porphyria-AIP, ALAD deficiency, hereditary coproporphyria-HCP, and porphyria variegata-VP) consists of potentially life-threatening neurovisceral attacks, for which givosiran, a novel and effective siRNA-based therapeutic, has recently been licensed. Nonetheless, the clinical manifestations of acute porphyrias are multifaceted and do not limit themselves to acute attacks. In particular, porphyria-associated kidney disease (PAKD) is a distinct, long-term degenerating condition with specific pathological and clinical features, for which a satisfactory treatment is not available yet. In PAKD, chronic tubule-interstitial damage has been most commonly reported, though other pathologic features (e.g., chronic fibrous intimal hyperplasia) are consistent findings. Given the relevant role of the kidney in porphyrin metabolism, the mechanisms possibly intervening in causing renal damage in AHPs are different: among others, δ-aminolevulinic acid (ALA)-induced oxidative damage on mitochondria, intracellular toxic aggregation of porphyrins in proximal tubular cells, and derangements in the delicate microcirculatory balances of the kidney might be implicated. The presence of a variant of the human peptide transporter 2 (PEPT2), with a greater affinity to its substrates (including ALA), might confer a greater susceptibility to kidney damage in patients with AHPs. Furthermore, a possible effect of givosiran in worsening kidney function has been observed. In sum, the diagnostic workup of AHPs should always include a baseline evaluation of renal function, and periodic monitoring of the progression of kidney disease in patients with AHPs is strongly recommended. This review outlines the role of the kidney in porphyrin metabolism, the available evidence in support of the current etiologic and pathogenetic hypotheses, and the known clinical features of renal involvement in acute hepatic porphyrias.

Role of Pharmacogenetics in Adverse Drug Reactions: An Update towards Personalized Medicine

Adverse drug reactions (ADRs) are an important and frequent cause of morbidity and mortality. ADR can be related to a variety of drugs, including anticonvulsants, anaesthetics, antibiotics, antiretroviral, anticancer, and antiarrhythmics, and can involve every organ or apparatus. The causes of ADRs are still poorly understood due to their clinical heterogeneity and complexity. In this scenario, genetic predisposition toward ADRs is an emerging issue, not only in anticancer chemotherapy, but also in many other fields of medicine, including hemolytic anemia due to glucose-6-phosphate dehydrogenase (G6PD) deficiency, aplastic anemia, porphyria, malignant hyperthermia, epidermal tissue necrosis (Lyell's Syndrome and Stevens-Johnson Syndrome), epilepsy, thyroid diseases, diabetes, Long QT and Brugada Syndromes. The role of genetic mutations in the ADRs pathogenesis has been shown either for dose-dependent or for dose-independent reactions. In this review, we present an update of the genetic background of ADRs, with phenotypic manifestations involving blood, muscles, heart, thyroid, liver, and skin disorders. This review aims to illustrate the growing usefulness of genetics both to prevent ADRs and to optimize the safe therapeutic use of many common drugs. In this prospective, ADRs could become an untoward "stress test," leading to new diagnosis of genetic-determined diseases. Thus, the wider use of pharmacogenetic testing in the work-up of ADRs will lead to new clinical diagnosis of previously unsuspected diseases and to improved safety and efficacy of therapies. Improving the genotype-phenotype correlation through new lab techniques and implementation of artificial intelligence in the future may lead to personalized medicine, able to predict ADR and consequently to choose the appropriate compound and dosage for each patient.

Patient and caregiver experiences of living with acute hepatic porphyria in the UK: a mixed-methods study

Background

This study used quantitative and qualitative research methods to analyze how acute hepatic porphyria (AHP) affects patients with varying annualized porphyria attack rates. The overall impact of AHP on patients and caregivers, including their quality of life, was explored. The nature and treatment of acute attacks, experiences of long-term heme arginate treatment and access to other appropriate treatment, and the extent of and treatment for chronic symptoms were also investigated within this study.

Methods

Patient and caregiver data were collected via an online survey of members of the British Porphyria Association, followed by an optional 1-h telephone interview.

Results

Thirty-eight patients and 10 caregivers responded to the survey. Of those, 10 patients and three caregivers completed follow-up interviews. Overall, 19 patients (50%) had experienced an acute attack within the previous 2 years, and the severity and types of symptoms experienced during or between acute attacks varied considerably. There were no clear definitions among patients for ‘mild’ or ‘severe’ attacks. Treatments and treatment settings used to manage attacks also varied. Following unsatisfactory care experiences at hospitals, some patients reported avoiding further hospital services for later attacks. Therefore, using settings of care as a measure of attack severity should be avoided. Ninety-four percent of patients also experienced chronic symptoms, which were as varied as acute attacks. Pain was the predominant chronic symptom and was managed with opioids in severe cases. Regardless of AAR, porphyria heavily impacted the daily lives of patients and caregivers. Although patients experiencing frequent attacks generally endured a greater impact on their daily life, patients with less frequent attacks also experienced impacts on all domains (social, leisure activities, relationship with family, relationships, psychological wellbeing, finances, employment, and study). Caregivers were most affected in the finance, relationships with family, and employment domains, and just over half of the caregivers reported a moderate impact on their psychological wellbeing.

Conclusions/implications

The burden of illness with AHP is high across all patients, regardless of frequency of attacks, and AHP negatively affects patients and caregivers alike.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01816-2.

Acute intermittent porphyria (AIP) in a patient with celiac disease

We present the case of an 18 year old Caucasian with known celiac disease, who suffered a severe first attack of acute intermittent porphyria (AIP) with neuropsychiatric symptoms, severe tetraparesis and respiratory insufficiency. Treatment with heme arginate and high-dose intravenous glucose and rigorous rehabilitation resulted in a slow but almost complete recovery of her motor symptoms. To our knowledge this is the first case of acute intermittent porphyria triggered by malnutrition in the context of celiac disease. It is remarkable that the patient showed a favourable outcome despite the severity of her initial symptoms. This case shows the importance of early and systematic symptomatic treatment in patients with severe neurologic manifestation of AIP.

Recent advances in the epidemiology and genetics of acute intermittent porphyria

Acute intermittent porphyria (AIP) is a dominant inherited disorder with a low penetrance that is caused by mutations in the gene coding for hydroxymethylbilane synthase (HMBS). Information about the epidemiology and molecular genetic features of this rare disorder is crucial to clinical research, and particularly to the evaluation of new treatments. Variations in the prevalence and penetrance of AIP in various studies may due to the different inclusion criteria and methods of assessment. Here, the prevalence and penetrance of AIP are analyzed systematically, and the genetic traits of different populations and findings regarding the genotype-phenotype correlation are summarized. In addition, quite a few studies have indicated that AIP susceptibility was affected by other factors, such as modifying genes. Findings regarding possible modifying genes are documented here, helping to reveal the pathogenesis of and treatments for AIP. The status of research on AIP in China reveals the lack of epidemiological and genetic studies of the Chinese population, a situation that needs to be promptly remedied.

Acute intermittent porphyria: focus on possible mechanisms of acute and chronic manifestations

Porphyrias are a group of inherited metabolic diseases that include eight types, each of which is caused by a mutation that affects an enzyme of the heme biosynthetic pathway. When an enzyme defect has physiological significance, it leads to overproduction of pathway precursors prior to the defective step. The partial absence of the third enzyme in the heme biosynthetic pathway, porphobilinogen deaminase (PBGD) also known as hydroxymethylbilane synthase (HMBS), results in acute intermittent porphyria (AIP), which affects mainly women. Subjects who had AIP symptoms were deemed to have manifest AIP (MAIP). Clinical manifestations are usually diverse and non-specific. Acute AIP episodes may present with abdominal pain, nausea, and vomiting, and repeated episodes may result in a series of chronic injuries. Therefore, studying the mechanisms of acute and chronic manifestations of AIP is of great significance. This review aims to summarize the possible mechanisms of acute and chronic manifestations in patients with AIP.

Detecting rare diseases in electronic health records using machine learning and knowledge engineering: Case study of acute hepatic porphyria

BACKGROUND

With the growing adoption of the electronic health record (EHR) worldwide over the last decade, new opportunities exist for leveraging EHR data for detection of rare diseases. Rare diseases are often not diagnosed or delayed in diagnosis by clinicians who encounter them infrequently. One such rare disease that may be amenable to EHR-based detection is acute hepatic porphyria (AHP). AHP consists of a family of rare, metabolic diseases characterized by potentially life-threatening acute attacks and chronic debilitating symptoms. The goal of this study was to apply machine learning and knowledge engineering to a large extract of EHR data to determine whether they could be effective in identifying patients not previously tested for AHP who should receive a proper diagnostic workup for AHP.

METHODS AND FINDINGS

We used an extract of the complete EHR data of 200,000 patients from an academic medical center and enriched it with records from an additional 5,571 patients containing any mention of porphyria in the record. After manually reviewing the records of all 47 unique patients with the ICD-10-CM code E80.21 (Acute intermittent [hepatic] porphyria), we identified 30 patients who were positive cases for our machine learning models, with the rest of the patients used as negative cases. We parsed the record into features, which were scored by frequency of appearance and filtered using univariate feature analysis. We manually choose features not directly tied to provider attributes or suspicion of the patient having AHP. We trained on the full dataset, with the best cross-validation performance coming from support vector machine (SVM) algorithm using a radial basis function (RBF) kernel. The trained model was applied back to the full data set and patients were ranked by margin distance. The top 100 ranked negative cases were manually reviewed for symptom complexes similar to AHP, finding four patients where AHP diagnostic testing was likely indicated and 18 patients where AHP diagnostic testing was possibly indicated. From the top 100 ranked cases of patients with mention of porphyria in their record, we identified four patients for whom AHP diagnostic testing was possibly indicated and had not been previously performed. Based solely on the reported prevalence of AHP, we would have expected only 0.002 cases out of the 200 patients manually reviewed.

CONCLUSIONS

The application of machine learning and knowledge engineering to EHR data may facilitate the diagnosis of rare diseases such as AHP. Further work will recommend clinical investigation to identified patients' clinicians, evaluate more patients, assess additional feature selection and machine learning algorithms, and apply this methodology to other rare diseases. This work provides strong evidence that population-level informatics can be applied to rare diseases, greatly improving our ability to identify undiagnosed patients, and in the future improve the care of these patients and our ability study these diseases. The next step is to learn how best to apply these EHR-based machine learning approaches to benefit individual patients with a clinical study that provides diagnostic testing and clinical follow up for those identified as possibly having undiagnosed AHP.

Acute Intermittent Porphyria: Current Perspectives And Case Presentation

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder characterized by a deficiency in heme biosynthesis. Heme biosynthesis occurs throughout the body, but it is most prominent in the erythroblastic system and liver. AIP is a hepatic porphyria whereby the liver is the source of toxic heme metabolites. Clinical manifestations of AIP result from a genetic mutation that leads to partial function of porphobiliogen deaminase (PBGD). This causes an accumulation of upstream, neurotoxic metabolites. Symptoms include but are not limited to peripheral neuropathies, autonomic neuropathies and psychiatric manifestations. AIP can be life threatening and clinical signs and symptoms are often heterogeneous and non-specific. Therefore, it is important to be able to recognize these patients to make a prudent diagnosis and offer appropriate therapy. Here, we review the epidemiology, pathophysiology, clinical presentation, diagnosis, and management of AIP including the role of liver transplantation.

Sclerodermalike syndromes: Great imitators

Sclerodermalike syndromes (SLSs) comprise diseases with mucin deposition (eg, scleromyxedema, scleredema), with eosinophilia (eg, eosinophilic fasciitis), metabolic or biochemical abnormalities (eg, nephrogenic systemic fibrosis), or endocrine disorders (eg, POEMS syndrome, or polyneuropathy, organomegaly, endocrinopathy, monoclonal lymphoproliferative disorder, and hypothyroidism). Chronic graft-versus-host disease may also show sclerodermalike skin changes. Inherited progeria syndromes with early aging (eg, Werner syndrome) and a heterogeneous group of hereditary disorders with either skin thickening (eg, stiff skin syndrome) or atrophy and tightening (eg, acrogeria) can also imitate classic systemic sclerosis (SSc). In addition, SLSs can be provoked by several drugs, chemicals, or even physical injury (eg, trauma, vibration stress, radiation). In SLSs, the distribution of skin involvement seems to be atypical compared with SSc. The acral skin involvement is usually missing, and lack of Raynaud phenomenon, scleroderma-specific antinuclear antibodies, the absence of scleroderma capillary pattern, and internal organ manifestations indicate the presence of an SLS. Skin involvement is sometimes nodular, and the underlying tissues can also be affected. For the differential diagnosis, a skin biopsy of the deeper layers including fascia and muscle is required. Histology does not always allow differentiation between SSc and SLSs; therefore, the diagnosis is often based on the distribution, quality of cutaneous involvement, and other accompanying clinical features.

Biomarkers for In Vivo Assessment of Transporter Function

Drug-drug interactions are a major concern not only during clinical practice, but also in drug development. Due to limitations of in vitro-in vivo predictions of transporter-mediated drug-drug interactions, multiple clinical Phase I drug-drug interaction studies may become necessary for a new molecular entity to assess potential drug interaction liabilities. This is a resource-intensive process and exposes study participants, who frequently are healthy volunteers without benefit from study treatment, to the potential risks of a new drug in development. Therefore, there is currently a major interest in new approaches for better prediction of transporter-mediated drug-drug interactions. In particular, researchers in the field attempt to identify endogenous compounds as biomarkers for transporter function, such as hexadecanedioate, tetradecanedioate, coproporphyrins I and III, or glycochenodeoxycholate sulfate for hepatic uptake via organic anion transporting polypeptide 1B or N¹-methylnicotinamide for multidrug and toxin extrusion protein-mediated renal secretion. We summarize in this review the currently proposed biomarkers and potential limitations of the substances identified to date. Moreover, we suggest criteria based on current experiences, which may be used to assess the suitability of a biomarker for transporter function. Finally, further alternatives and supplemental approaches to classic drug-drug interaction studies are discussed.

Psychiatric Aspects of Acute Porphyria: a Comprehensive Review

PURPOSE OF REVIEW

The aim of this paper is to review psychiatric manifestations, comorbidities, and psychopharmacological management in individuals with acute porphyria (AP).

RECENT FINDINGS

Recent literature begins to clarify associations between AP, schizophrenia, bipolar disorder, and other psychopathology. Broad psychiatric symptoms have been associated to acute porphyria (AP) and correspond to a spectrum of heterogeneous manifestations such as anxiety, affective alterations, behavioral changes, personality, and psychotic symptoms. These symptoms may be difficult to identify as being related to porphyria since symptoms may arise at any time during the disease process. In addition, these patients may present psychiatric conditions secondary to the disease, such as adjustment disorder and substance use disorders. Timely diagnosis and appropriate treatment of psychiatric manifestations positively impact the course of the disease.

Porphyria and kidney diseases

The kidneys, after the bone marrow and liver, are third in terms of the amounts of haem synthesized daily. Haem is incorporated into haemoproteins that are critical to renal physiology. In turn, disturbances in haem metabolism interfere with renal physiology and are tightly interrelated with kidney diseases. Acute intermittent porphyria causes kidney injury, whereas medical situations associated with end-stage renal disease, such as porphyrin accumulation, iron overload and hepatitis C, participate in the inhibition of uroporphyrinogen decarboxylase and predispose the individual to porphyria cutanea tarda. Even if some of these interactions have been known for a long time, the clinical situations associated with these interrelations have strikingly evolved over time with the advent of new therapeutic strategies for dialysis therapy and a better understanding of the pathophysiological mechanisms of porphyria-associated kidney disease. Physicians should be aware of these interactions. The aim of this review is to summarize the complex interactions between kidney physiology and pathology in the settings of porphyria and to emphasize their often-underestimated importance.

Secret Underlying Unexplained Abdominal Pain, Neurological Symptoms and Intermittent Hypertension: Acute Intermittent Porphyria

A 21-year-old female patient with abdominal pain, vomiting and constipation was admitted to the hospital with the possible diagnosis of diabetic ketoacidosis. Due to increased abdominal pain and constipation the patient underwent a surgery with the diagnosis of ileus. However, no pathological findings were found in the abdominal organs apart from serous fluid in the abdominal cavity. The patient became hypertensive, tachycardic and had an episode of seizures postoperatively. Neurological manifestations with unexplained abdominal pain indicated a diagnosis of acute intermittent porphyria (AIP). Acute intermittent porphyria diagnosis is based on elevated urinary δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) levels as well as hydroxymethylbilane synthase (HMBS) IVS13-2 A>G heterozygous mutation. Familial Mediterranean Fever (FMF) gene mutations were not confirmed. Porphyria should be considered in the differential diagnosis of patients with recurrent abdominal pain, neurological symptoms and lack of FMF gene polymorphism.

Dermatologic Manifestations of Chronic Hepatitis C Infection

Chronic hepatitis C virus (HCV) infection is associated with various extrahepatic manifestations, including dermatologic involvement mostly caused by immune complexes. Mixed cryoglobulinemia has a strong relationship with HCV with 95% of these patients being infected with HCV. Lichen planus is a disease of the squamous epithelium and may affect any part of the skin, with 4% to 24% of patients with lichen planus reported to have chronic HCV infection. Porphyria cutanea tarda is the most common form of porphyria, and it is thought that HCV interferes with iron stores, which can promote porphyria cutanea tarda. Finally, necrolytic acral erythema is a rare, psoriasis-like disease closely associated with HCV.

Chemical-induced coordinated and reciprocal changes in heme metabolism, cytochrome P450 synthesis and others in the liver of humans and rodents

A wide variety of drugs and chemicals have been shown to produce induction and inhibition of heme-metabolizing enzymes, and of drug-metabolizing enzymes, including cytochrome P450s (P450s, CYPs), which consist of many molecular species with lower substrate specificity. Such chemically induced enzyme alterations are coordinately or reciprocally regulated through the same and/or different signal transductions. From the toxicological point of view, these enzymatic changes sometimes exacerbate inherited diseases, such as precipitation of porphyrogenic attacks, although the induction of these enzymes is dependent on the animal species in response to the differences in the stimuli of the liver, where they are also metabolized by P450s. Since P450s are hemoproteins, their induction and/or inhibition by chemical compounds could be coordinately accompanied by heme synthesis and/or inhibition. This review will take a retrospective view of research works carried out in our department and current findings on chemical-induced changes in hepatic heme metabolism in many places, together with current knowledge. Specifically, current beneficial aspects of induction of heme oxygenase-1, a rate-limiting heme degradation enzyme, and its relation to reciprocal and coordinated changes in P450s, with special reference to CYP2A5, in the liver are discussed. Mechanistic studies are also summarized in relation to current understanding on these aspects. Emphasis is also paid to an example of a single chemical compound that could cause various changes by mediating multiple signal transduction systems. Current toxicological studies have been developing by utilizing a sophisticated "omics" technology and survey integrated changes in the tissues produced by the administration of a chemical, even in time- and dose-dependent manners. Toxicological studies are generally carried out step by step to determine and elucidate mechanisms produced by drugs and chemicals. Such approaches are correct; however, current "omics" technology can clarify overall changes occurring in the cells and tissues after treating animals with drugs and chemicals, integrate them and discuss the results. In the present review, we will discuss chemical-induced similar changes of heme synthesis and degradation, and of P450s and finally convergence to similar or different directions.