Recent advances in the epidemiology and genetics of acute intermittent porphyria

A case report of acute intermittent porphyria leading to severe disability

Acute intermittent porphyria (AIP) is a rare inherited metabolic disorder resulting from increased production of porphyrins and their precursors, δ-aminolevulinic acid (ALA) and porphobilinogen (PBG), due to deficiencies in the enzymatic activity of the heme synthesis pathway. The disease is typically characterized by a triad of abdominal pain, neurologic impairment symptoms, and psychiatric abnormalities. However, only a small percentage of patients present with this classic triad of symptoms. Our female patient, aged 23, was admitted to the hospital with a 4-year history of abnormal mood episodes and weakness in the limbs for over 1 week. She had a previous medical history of intestinal obstruction. After admission, a cranial MRI revealed reversible posterior leukoencephalopathy imaging manifestations, and the patient exhibited weakness of the extremities, respiratory failure, seizures, and severely reduced serum sodium concentration. The diagnosis of AIP was ultimately confirmed by a positive urine PBG-sunlight test and analysis of HMBS gene variants. The absence of typical triadic signs in acute attacks of AIP can make early recognition of the disease challenging. We present a case with multiple typical clinical manifestations of AIP in the hope of aiding clinicians in fully recognizing acute intermittent porphyria.

The diagnosis of acute intermittent porphyria combined with seizures: Case report

RATIONALE

Acute intermittent porphyria (AIP) is a rare metabolic disorder affecting heme production due to enzyme porphobilinogen deaminase deficiency. Diagnosing acute intermittent porphyria is difficult because its symptoms interrelate with those of other common diseases. When AIP is combined with seizures, the diagnosis process is more complicated. This case report shows all tests and criteria used to arrive at the final stage of diagnosis.

PATIENT CONCERNS

The patient complained of severe abdominal pain, nausea, vomiting, and intermittent convulsions. Her medical history shows she had abdominal pain, mainly dull pain in the left upper abdomen.

DIAGNOSES

Different symptomatic tests were done, and the cause of her symptoms was uncertain. A urine sun drying test was then done and confirmed the presence of porphyrin used to diagnose AIP. A genetic test was done after the patient was discharged, and AIP diagnosis was confirmed.

INTERVENTIONS

Acute intermittent porphyria treatment was administered.

OUTCOMES

The patent recovered fully.

LESSONS

It is essential to consider acute intermittent porphyria diagnosis in patients having unexplained severe abdominal pain associated with neurological and psychiatric symptoms. Since AIP is a rare disease with a high mortality rate when not treated early, Clinical practices should include AIP as one of the tests done on patients showing these symptoms at an early stage. The fastest way to identify this is to conduct a urine test. The change of color from brown to reddish color is a diagnostic indicator of AIP. This strategy helps reduce misdiagnoses and delayed treatment of the right disease.

A novel mutation c.457C > T p.Q153 in the HMBS gene in a Mexican woman with acute intermittent porphyria

Key Clinical Message

The detection of a novel HMBS gene mutation (c.457C > T) in a Mexican woman with acute intermittent porphyria underscores the importance of expanding genetic analyses in diverse populations to improve diagnosis, management, and knowledge of the disease's clinical implications.

Abstract

Acute intermittent porphyria (AIP) is an autosomal dominant disorder caused by a deficiency in the enzymatic activity of porphobilinogen deaminase (HMBS), resulting in the accumulation of toxic heme metabolites. In this report, we present the case of a Mexican woman with AIP who experienced recurrent episodes of severe abdominal pain, weakness, vomiting, and insomnia. Despite the challenges in diagnosis and treatment, genetic analysis revealed a novel HMBS mutation, c.457C > T (p.Q153X), located in exon 9. This mutation induces a premature translational stop codon and had not been previously reported in medical literature among individuals with AIP. Remarkably, the patient exhibited a positive response to RNA interference therapy. We hypothesize that this novel HMBS mutation may potentially account for the more severe clinical presentation observed in this case. However, further research is necessary to establish a definitive link between this specific mutation and disease severity. The prevalence and genetic variants of AIP in Mexico remain largely unknown, underscoring the importance of conducting additional research and expanding genetic analyses to gain a better understanding of the clinical implications associated with these mutations.

Mitochondrial DNA Copy Number Drives the Penetrance of Acute Intermittent Porphyria

No published study has investigated the mitochondrial count in patients suffering from acute intermittent porphyria (AIP). In order to determine whether mitochondrial content can influence the pathogenesis of porphyria, we measured the mitochondrial DNA (mtDNA) copy number in the peripheral blood cells of 34 patients and 37 healthy individuals. We found that all AIP patients had a low number of mitochondria, likely as a result of a protective mechanism against an inherited heme synthesis deficiency. Furthermore, we identified a close correlation between disease penetrance and decreases in the mitochondrial content and serum levels of PERM1, a marker of mitochondrial biogenesis. In a healthy individual, mitochondrial count is usually modulated to fit its ability to respond to various environmental stressors and bioenergetic demands. In AIP patients, coincidentally, the phenotype only manifests in response to endogenous and exogenous triggers factors. Therefore, these new findings suggest that a deficiency in mitochondrial proliferation could affect the individual responsiveness to stimuli, providing a new explanation for the variability in the clinical manifestations of porphyria. However, the metabolic and/or genetic factors responsible for this impairment remain to be identified. In conclusion, both mtDNA copy number per cell and mitochondrial biogenesis seem to play a role in either inhibiting or promoting disease expression. They could serve as two novel biomarkers for porphyria.

Acute Intermittent Porphyria: A Review and Rehabilitation Perspective

Acute intermittent porphyria (AIP) is an uncommon metabolic disease that impacts multiple organs and can manifest in many ways. It is often misdiagnosed due to its nonspecific symptoms. Neurovisceral signs and symptoms should alert physicians to consider AIP in the differential after excluding more common causes. Identifying the underlying cause is critical in preventing acute attacks, and trigger avoidance is the optimal approach to managing AIP. Medications that are contraindicated should be reviewed thoroughly. Prompt intravenous hematin administration is the primary treatment for acute attacks, and additional pharmacological therapies may be necessary to treat concurrent symptoms. A severe neurological manifestation of AIP is flaccid paralysis or severe motor weakness, which can develop into total quadriplegia and respiratory insufficiency. A comprehensive rehabilitation program is an integral aspect of the treatment plan. Since the incidence of this disease is low, functional prognosis is not well-known. As a result, it is challenging to determine the most appropriate structure, intensity, and duration of rehabilitation therapy. By extending the treatment plan, individuals with tetraplegia due to AIP can continue to make functional gains years after the onset of weakness. Understanding the disease's functional prognosis will aid in coordinating resources and improving healthcare expenditures.

[Acute hepatic porphyrias]

Acute porphyrias are caused by rare hereditary disorders of hepatic heme biosynthesis. Episodes of accumulating neurotoxic metabolites lead to multisystemic symptoms such as visceral pain, autonomic dysregulation, neurocognitive impairment, hyponatremia, and occasionally motor paralysis. In addition to protracted non-emergency courses, acute life-threatening crises can occur, often triggered by infection, medication, fasting, or hormonal stimuli. Since the clinical presentation is nonspecific and multifaceted, many patients have gone through a long odyssey until they receive a diagnosis. Acute attacks often lead to presenting initially to the emergency department, where acute hepatic porphyria (AHP) is easily overlooked in the differential diagnosis. Establishing the diagnosis requires a high level of genuine suspicion (e.g., cluster of signs and symptoms along with certain patterns of health care resource utilization). The initial diagnostic work-up requires the measurement of metabolites in the urine. Emergency management consists of infusions of glucose and heme arginate along with symptomatic therapy. However, porphyrinogenic agents must be strictly avoided ( www.drugs-porphyria.org ). After initial diagnosis, a thorough work-up should be done at a porphyria center (confirming the diagnosis, education, genetic counselling) and issuance of an emergency identification card is mandatory. If the frequency of relapses is high, new targeted prophylactic therapies have proven effective. Patients with known porphyria require special attention in any acute medical condition in order to avoid porphyrinogenic triggers and to exclude threatening differential diagnosis (e.g., sepsis) by consistent basic diagnostics.

Novel hydroxymethylbilane synthase gene mutation identified and confirmed in a woman with acute intermittent porphyria: A case report

BACKGROUND

Acute intermittent porphyria (AIP) is a rare autosomal dominant porphyrin metabolic disease caused by a mutation in the hydroxymethylbilane synthase(HMBS) gene. This study aimed to explore the clinical manifestations of a patient with AIP, to identify a novel HMBS gene mutation in the proband and some of her family members, and to confirm the pathogenicity of the variant.

CASE SUMMARY

A 22-year-old Chinese woman developed severe abdominal pain, lumbago, sinus tachycardia, epileptic seizure, hypertension, and weakness in lower limbs in March, 2018. Biochemical examinations indicated hypohepatia and hyponatremia. Her last menstrual period was 45 d prior to admission, and she was unaware of the pregnancy, which was confirmed by a pregnancy test after admission. Sunlight exposure of her urine sample for 1 h turned it from yellow to wine red. Urinary porphyrin test result was positive. Based on these clinical manifestations, AIP was diagnosed. After increasing her daily glucose intake (250–300 g/d), abdominal pain was partially relieved. Three days after hospitalization, spontaneous vaginal bleeding occurred, which was confirmed as spontaneous abortion; thereafter, her clinical symptoms completely resolved. Genetic testing revealed a novel heterozygous splicing variant of the HMBS gene in exon 10 (c.648_651+1delCCAGG) in the proband and four other family members. The pathogenicity of the variant was verified through bioinformatic methods and a minigene assay.

CONCLUSION

We identified a novel HMBS gene mutation in a Chinese patient with AIP and confirmed its pathogenicity.

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.

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.

A Perfect Storm: Abdominal Pain and Ileus Explained by Acute Intermittent Porphyria Caused by Prehospitalization and Intrahospitalization Factors

Acute intermittent porphyria (AIP) is a rare autosomal dominant inherited disease, predominantly seen in female patients, caused by mutations in the hydroxymethylbilane synthase gene. When impaired, elevated heme biosynthesis precursor levels accumulate in the liver, resulting in neurological symptoms, psychiatric disturbances, darkened urine color, abdominal pain, nausea, vomiting, and ileus. We present a 22-year-old Hispanic female with diffuse abdominal pain and no bowel movements for 8 days. She reported recent antibiotic and oral contraceptive pill use. Computerized tomography of her abdomen revealed a dilated small bowel and marked colonic distension. A colonoscopy found mild nonspecific inflammation in the rectosigmoid and terminal ileum. Her abdominal pain persisted despite interventions and improvements in appetite, bowel movements, abdominal imaging, and treatment of an identified Clostridium difficile infection. A random urine porphobilinogen was then obtained and found to be elevated. Fractionation of plasma and urine porphyrins was suggestive of AIP. Her symptoms improved with 3 days of intravenous (IV) hematin and IV dextrose. This is a unique case of a rare disease due to her clinical presentation with ileus, unremarkable past medical history, family history, and the prehospitalization and intrahospitalization factors that likely exacerbated the patient AIP.

Unexpected presentation of acute porphyria

Acute porphyrias are rarely reported in Southeast Asia. They may be underdiagnosed due to their clinical mimicry and lack of awareness among physicians. There is a common cognitive bias to gravitate towards common conditions. In this case report, a 28-year-old woman, who presented with seizures, rhabdomyolysis hyponatraemia and altered mental state, was initially diagnosed as amphetamine overdose. She had presented 3 days prior with abdominal pain, treated for acute cystitis and discharged. On readmission for seizures a day later, she was extensively worked up for altered mental state. Despite normalisation of serum sodium concentration and control of her seizures, she remained unwell. Further investigations later confirmed a diagnosis of acute porphyria. The aim of this case report is to highlight the non-specific nature of presentation of acute porphyria and the importance of considering it as a differential diagnosis in cases of abdominal pain with neuropsychiatric features.