Acute porphyrias: a German monocentric study of the biochemical, molecular genetic, and clinical data of 62 families

A high urinary urobilinogen/serum total bilirubin ratio indicates acute hepatic porphyria in patients with abdominal pain

Acute hepatic porphyria (AHP) has always been a diagnostic dilemma for physicians due to its variable symptoms. Correct diagnosis mainly depends on the detection of an elevated urinary porphobilinogen (PBG), which is not a routine test and highly relies on the physician's awareness of AHP. In the present study, we identified a more convenient indicator during routine examinations to improve the diagnosis of AHP. We found that AHP patients showed a significant higher "FALSE" urinary urobilinogen level caused by urinary PBG during the urinalysis when detected by strips impregnated with Ehrlich reagent (P < 0.05). And a remarkable increase in the urinary urobilinogen/serum total bilirubin ratio was observed in AHP patients. The area under the ROC curve of this ratio for AHP was 1.000 (95% confidence interval 1.000-1.000, P < 0.01). A cutoff value of 3.22 for this ratio yielded a sensitivity of 100% and a specificity of 100% to distinguish AHP patients from the controls. Thus, we proved that a "falsely" high urinary urobilinogen level that was adjusted by the serum total bilirubin level (urinary urobilinogen/serum total bilirubin ratio) could be used as a sensitive and specific screening marker for AHP in patients with abdominal pain.

Heterogeneous molecular behavior in liver tumors (HCC and CCA) of two patients with acute intermittent porphyria

INTRODUCTION

Acute intermittent porphyria (AIP) is a very rare (orphan) metabolic disorder of porphyrin biosynthesis which is characterized by elevated plasma and urine levels of 5-aminolevulinic acid (5-ALA) and porphobilinogen (PBG). Patients with this disorder which is caused by a germline mutation of the hydroxymethylbilan-synthase (HMBS)-gene have a high risk of primary liver cancer which may be determined by disease activity. The exact mechanism of carcinogenesis of this rare tumor is unknown, however.

MATERIALS AND METHODS

We analyzed paraffin-embedded formalin-fixed liver tumor and normal liver specimens of two female AIP patients treated at the Munich EPNET center. One patient had developed hepatocellular carcinoma (HCC), the other intrahepatic cholangiocarcinoma (CCA). Since biallelic inactivation of HMBS had been observed in one study, we used Sanger and next-generation sequencing with a 8 gene porphyria panel plus 6 potential modifier loci to search for mutations in DNA extractions.

RESULTS

In the patient with the HCC, we found a second inactivating mutation in the HMBS gene in the tumor but not in the adjacent normal liver tissue. No mutation could be found in the liver tissues of the patient with CCA, however.

CONCLUSIONS

Biallelic inactivation of HMBS or protoporphyrinogen-oxidase (PPOX), another enzyme of porphyrin biosynthesis, has been observed in patients with acute porphyrias and liver tumors. We could confirm this in our patient with HCC with a mutation in HMBS but not in the one with CCA. Since 5-ALA can be converted into carcinogenic substances such as 4,5-dioxovaleric acid (DOVA) or 3,6-dihydropyrazine-2,5-dipropanoic acid (= cyclic dimerization product of 5-ALA), local production of these metabolites in hepatic areas with complete loss of HMBS activity may contribute to liver carcinogenesis.

Therapy Follows Diagnosis: Old and New Approaches for the Treatment of Acute Porphyrias, What We Know and What We Should Know

Heme, iron protoporphyrin IX, is one of life’s most central molecules. Hence, availability of the enzymatic machinery necessary for its synthesis is crucial for every cell. Consequently, inborn errors of porphyrin metabolism that compromise normal synthesis, namely the family of porphyrias, undermine normal cellular metabolism given that heme has functions in catalytic centers, signal transduction and functional regulation and its synthesis is fully integrated into the center of intermediary metabolism. Very often, diagnosis of porphyrias is difficult and therefore delayed. Therapy can be as complicated. Over the last 50 years, several strategies have been developed: because of its integration with other parts of intermediary metabolism, the infusion of glucose (glucose effect) was one of the first attempts to counterbalance the dysregulation of porphyrin synthesis in porphyrias. Since heme synthesis is impaired, infusional replacement of heme was the next important therapeutic step. Recently, siRNA technology has been introduced in order to downregulate 5-ALA-synthase 1, which contributes to the patho-physiology of these diseases. Moreover, other novel therapies using enzyme protein replacement, mRNA techniques or proteostasis regulators are being developed.

Psychological Aspect and Quality of Life in Porphyrias: A Review

The World Health Organization (WHO) describes “health” as a state of physical, mental, and social well-being and not merely the absence of disease or infirmity. Therefore, a biopsychosocial approach should be considered as an integral part of patients’ management. In this review, we summarize the available data starting from 1986 on the biological, psychological, and social aspects of porphyrias in order to provide a useful tool for clinicians about the missing knowledge within this field. Porphyrias are a group of rare metabolic disorders affecting the heme biosynthetic pathway and can be categorized into hepatic and erythropoietic. Here, a total of 20 articles reporting the psychological and the quality of life (QoL) data of porphyria patients affected by acute hepatic porphyrias (AHPs), Porphyria Cutanea Tarda (PCT), and Erythropoietic Protoporphyria (EPP) were analyzed. These 13 articles include reported quantitative methods using questionnaires, while the reaming articles employed qualitative descriptive approaches through direct interviews with patients by psychology professionals. We conclude that the use of questionnaires limits the complete description of all areas of a patient’s life compared to a direct interview with specialists. However, only a combined use of these methods could be the best approach for the correct disorder management.

Givosiran in acute intermittent porphyria: A personalized medicine approach

BACKGROUND

In patients with acute intermittent porphyria (AIP), induction of delta aminolevulinic acid synthase 1 (ALAS1) leads to haem precursor accumulation that may cause recurring acute attacks. In a recent phase III trial, givosiran significantly reduced the attack rate in severe AIP patients. Frequent adverse events were injection-site reaction, fatigue, nausea, chronic kidney disease and increased alanine aminotransferase.

OBJECTIVES

To describe the efficacy and safety of givosiran based on a personalized medical approach.

METHODS

We conducted a retrospective patient file study in 25 severe AIP patients treated with givosiran in France. We collected data on clinical and biochemical efficacy along with reports of adverse events.

RESULTS

Givosiran drastically reduced the attack rate in our cohort, as 96% were attack-free at the time of the study. The sustained efficacy of givosiran in most patients allowed us to personalize dosing frequency. In 42%, givosiran was only given when haem precursor levels were increasing. Our data suggest that givosiran is most effective when given early in the disease course. We confirmed a high prevalence of adverse events. One patient discontinued treatment due to acute pancreatitis. All patients had hyperhomocysteinemia, and all patients with initial homocysteine levels available showed an increase under treatment. In this context, one patient was diagnosed with pulmonary embolism.

CONCLUSION

The sustained effect of givosiran allowed a decrease in dosing frequency without compromising treatment efficacy. The high prevalence of adverse events emphasizes the importance of restricting the treatment to severe AIP and administering the minimum effective dose for each patient.

Severe homocysteinemia in two givosiran-treated porphyria patients: is free heme deficiency the culprit?

Givosiran is a novel approach to treat patients with acute intermittent porphyrias (AIP) by silencing of ∂-ALA-synthase 1, the first enzyme of heme biosynthesis in the liver. We included two patients in the Envision study who responded clinically well to this treatment. However, in both patients, therapy had to be discontinued because of severe adverse effects: One patient (A) developed local injection reactions which continued to spread all over her body with increasing number of injections and eventually caused a severe systemic allergic reaction. Patient B was hospitalized because of a fulminant pancreatitis. Searching for possible causes, we also measured the patients plasma homocysteine (Hcy) levels in fluoride-containing collection tubes: by LC-MS/MS unexpectedly, plasma Hcy levels were 100 and 200 in patient A and between 100 and 400 μmol/l in patient B. Searching for germline mutations in 10 genes that are relevant for homocysteine metabolism only revealed hetero- and homozygous polymorphisms in the MTHFR gene. Alternatively, an acquired inhibition of cystathionine-beta-synthase which is important for homocysteine metabolism could explain the plasma homocysteine increase. This enzyme is heme-dependent: when we gave heme arginate to our patients, Hcy levels rapidly dropped. Hence, we conclude that inhibition of ∂-ALA-synthase 1 by givosiran causes a drop of free heme in the hepatocyte and therefore the excessive increase of plasma homocysteine. Hyperhomocysteinemia may contribute to the adverse effects seen in givosiran-treated patients which may be due to protein-N-homocysteinylation.

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.