Long-term complications in acute porphyria.

New treatment options and low attack-related mortality have changed the life expectancy of patients with acute porphyria (AP) to that of the general population. Clinicians should therefore be aware of the long-term complications of AP, which typically include chronic neuropathy and encephalopathy, high blood pressure and porphyria-associated kidney disease. Patients have an increased risk of primary liver cancer (PLC), but no increased risk of non-hepatic cancers. Chronic pain occurs in patients with recurrent attacks, combined with chronic fatigue and nausea, leading to poor quality of life. Patients with sporadic attacks may also have chronic symptoms, which should be distinguished from mild recurrent attacks and treated appropriately. Sequels of acute polyneuropathy after an attack should be distinguished from ongoing chronic polyneuropathy, as the management is different. Overestimation of chronic neuropathy or encephalopathy caused by AP should be avoided, and other causes should be treated accordingly. Prevention of recurrent attacks is the best strategy for managing chronic comorbidities and should be actively accomplished. Hormonal interventions in female patients, or in severe cases, prophylactic givosiran or haematin, may be helpful before liver transplantation to prevent recurrent attacks. Regular monitoring can be personalised according to the patient's age, comorbidities and AP activity. Blood pressure, renal function and cardiovascular risk factors should be monitored annually in patients with previous symptoms. Appropriate medication and lifestyle management, including nutrition and hydration, are necessary to prevent complications. As PLC is common, especially in patients with acute intermittent porphyria, bi-annual surveillance after the age of 50 is important.

Systematically testing human HMBS missense variants to reveal mechanism and pathogenic variation.

Defects in hydroxymethylbilane synthase (HMBS) can cause acute intermittent porphyria (AIP), an acute neurological disease. Although sequencing-based diagnosis can be definitive, ∼⅓ of clinical HMBS variants are missense variants, and most clinically reported HMBS missense variants are designated as "variants of uncertain significance" (VUSs). Using saturation mutagenesis, en masse selection, and sequencing, we applied a multiplexed validated assay to both the erythroid-specific and ubiquitous isoforms of HMBS, obtaining confident functional impact scores for >84% of all possible amino acid substitutions. The resulting variant effect maps generally agreed with biochemical expectations and provide further evidence that HMBS can function as a monomer. Additionally, the maps implicated specific residues as having roles in active site dynamics, which was further supported by molecular dynamics simulations. Most importantly, these maps can help discriminate pathogenic from benign HMBS variants, proactively providing evidence even for yet-to-be-observed clinical missense variants.

Systematically testing human HMBS missense variants to reveal mechanism and pathogenic variation.

Defects in hydroxymethylbilane synthase (HMBS) can cause Acute Intermittent Porphyria (AIP), an acute neurological disease. Although sequencing-based diagnosis can be definitive, ~⅓ of clinical HMBS variants are missense variants, and most clinically-reported HMBS missense variants are designated as "variants of uncertain significance" (VUS). Using saturation mutagenesis, en masse selection, and sequencing, we applied a multiplexed validated assay to both the erythroid-specific and ubiquitous isoforms of HMBS, obtaining confident functional impact scores for >84% of all possible amino-acid substitutions. The resulting variant effect maps generally agreed with biochemical expectation. However, the maps showed variants at the dimerization interface to be unexpectedly well tolerated, and suggested residue roles in active site dynamics that were supported by molecular dynamics simulations. Most importantly, these HMBS variant effect maps can help discriminate pathogenic from benign variants, proactively providing evidence even for yet-to-be-observed clinical missense variants.

Pathogenesis of acute encephalopathy in acute hepatic porphyria.

Acute encephalopathy (AE) can be a manifestation of an acute porphyric attack. Clinical data were studied in 32 patients during AE with or without polyneuropathy (PNP) together with 12 subjects with PNP but no AE, and 17 with dysautonomia solely. Brain neuroimaging was done in 20 attacks during AE, and PEPT2 polymorphisms were studied in 56 subjects, 24 with AE. AE manifested as a triad of seizures, confusion and/or blurred vision. Symptoms lasting 1-5 days manifested 3-19 days from the onset of an attack. 55% of these patients had acute PNP independent of AE. Posterior reversible encephalopathy syndrome (PRES) was detected in 42% of the attacks. These patients were severely affected and hyponatremic (88%). Reversible segmental vasoconstriction was rare. There was no statistical difference in hypertension or urinary excretion of porphyrin precursors among the patients with or without AE. In 94% of the attacks with AE, liver transaminases were elevated significantly (1.5 to fivefold, P = 0.034) compared to a normal level in 87% of the attacks with dysautonomia, or in 25% of patients with PNP solely. PEPT2*2/2 haplotype was less common among patients with AE than without (8.3% vs. 25.8%, P = 0.159) and in patients with PNP than without (9.5% vs. 22.9%, P = 0.207), suggesting a minor role, if any, in acute neurotoxicity. In contrast, PEPT2*2/2 haplotype was commoner among patients with chronic kidney disease (P = 0.192). Acute endothelial dysfunction in porphyric encephalopathy could be explained by a combination of abrupt hypertension, SIADH, and acute metabolic and inflammatory factors of hepatic origin.

Pain in acute hepatic porphyrias: Updates on pathophysiology and management.

Acute hepatic porphyrias (AHPs) typically present with recurrent acute attacks of severe abdominal pain and acute autonomic dysfunction. While chronic symptoms were historically overlooked in the literature, recent studies have reported increased prevalence of chronic, mainly neuropathic, pain between the attacks. Here we characterize acute and chronic pain as prominent manifestations of the AHPs and discuss their pathophysiology and updated management. In addition to the severe abdominal pain, patients could experience low back pain, limb pain, and headache during acute attacks. Chronic pain between the attacks is typically neuropathic and reported mainly by patients who undergo recurrent attacks. While the acute abdominal pain during attacks is likely mediated by autonomic neuropathy, chronic pain likely represents delayed recovery of the acute neuropathy with ongoing small fiber neuropathy in addition to peripheral and/or central sensitization. δ-aminolaevulinic acid (ALA) plays a major role in acute and chronic pain via its neurotoxic effect, especially where the blood-nerve barrier is less restrictive or absent i.e., the autonomic ganglia, nerve roots, and free nerve endings. For earlier diagnosis, we recommend testing a spot urine porphobilinogen (PBG) analysis in any patient with recurrent severe acute abdominal pain with no obvious explanation, especially if associated with neuropathic pain, hyponatremia, autonomic dysfunction, or encephalopathy. Of note, it is mandatory to exclude AHPs in any acute painful neuropathy. Between the attacks, diagnostic testing for AHPs should be considered for patients with a past medical history of acute/subacute neuropathy, frequent emergency room visits with abdominal pain, and behavioral changes. Pain during the attacks should be treated with opiates combined with hemin infusions. Symptomatic treatment of chronic pain should start with gabapentinoids and certain antidepressants before opiates. Givosiran reduces levels of ALA and PBG and likely has long-term benefits for chronic pain, especially if started early during the course of the disease.

An update of clinical management of acute intermittent porphyria.

Acute intermittent porphyria (AIP) is due to a deficiency of the third enzyme, the hydroxymethylbilane synthase, in heme biosynthesis. It manifests with occasional neuropsychiatric crises associated with overproduction of porphyrin precursors, aminolevulinic acid and porphobilinogen. The clinical criteria of an acute attack include the paroxysmal nature and various combinations of symptoms, such as abdominal pain, autonomic dysfunction, hyponatremia, muscle weakness, or mental symptoms, in the absence of other obvious causes. Intensive abdominal pain without peritoneal signs, acute peripheral neuropathy, and encephalopathy usually with seizures or psychosis are the key symptoms indicating possible acute porphyria. More than fivefold elevation of urinary porphobilinogen excretion together with typical symptoms of an acute attack is sufficient to start a treatment. Currently, the prognosis of the patients with AIP is good, but physicians should be aware of a potentially fatal outcome of the disease. Mutation screening and identification of type of acute porphyria can be done at the quiescent phase of the disease. The management of patients with AIP include following strategies: A, during an acute attack: 1) treatment with heme preparations, if an acute attack is severe or moderate; 2) symptomatic treatment of autonomic dysfunctions, polyneuropathy and encephalopathy; 3) exclusion of precipitating factors; and 4) adequate nutrition and fluid therapy. B, during remission: 1) exclusion of precipitating factors (education of patients and family doctors), 2) information about on-line drug lists, and 3) mutation screening for family members and education about precipitating factors in mutation-positive family members. C, management of patients with recurrent attacks: 1) evaluation of the lifestyle, 2) evaluation of hormonal therapy in women, 3) prophylactic heme therapy, and 4) liver transplantation in patients with severe recurrent attacks. D, follow-up of the AIP patients for long-term complications: chronic hypertension, chronic kidney insufficiency, chronic pain syndrome, and hepatocellular carcinoma.

Is screening for urinary porphobilinogen useful among patients with acute polyneuropathy or encephalopathy?

Acute porphyrias are a group of inherited metabolic disorders representing overproduction syndromes with the formation of neurotoxic haem precursors. Clinical manifestations consist of acute attacks, which include abdominal pain, dysautonomia, mental symptoms, polyneuropathy and seizures mimicking many other acute neurological disorders.Porphyrin metabolites were screened in 108 patients with acute polyneuropathy or encephalopathy associated with pain and/or dysautonomia, who attended neurological wards, in order to evaluate the number of patients with acute porphyria.Urinary porphyrins and their precursors were increased in 21% of the cases. Surprisingly many patients (11%) had previously undiagnosed acute porphyria. Half of these patients had had mild to moderate symptoms of acute porphyria previously. Secondary porphyrinuria, which was mainly transient coproporphyrinuria because of hepatopathy, was also common (10%). Of the 108 patients studied, the levels of urinary porphyrins or their precursors were normal in the majority (79%) of the cases, who commonly had Guillain-Barré syndrome (40%). Epileptic seizures were also frequent (18%), but none of the patients with acute porphyria had solely epileptic seizures without prolonged confusion (>or= 1 day).Based on our findings, acute inherited porphyria is not infrequent among the selected group of neurological patients and screening of urinary PBG is cost-beneficial. Since the correct diagnosis of a hereditary disease is essential, genetic screening should be performed whenever possible for patients with clinically and biochemically confirmed acute porphyria.

Nine mutations including three novel mutations among Russian patients with acute intermittent porphyria.

Acute intermittent porphyria (AIP) is a metabolic disease due to a partial deficiency of hydroxymethylbilane synthase (HMBS) in heme biosynthesis. Direct sequencing of genomic DNA samples of 11 unrelated Russian AIP patients, 32 of their relatives and 50 healthy controls from northwestern Russia including Saint Petersburg revealed nine mutations in the HMBS gene. Three novel mutations, c.825+5G>C, c.825+3_825+6del, and c.770T>C, resulted in varying amounts of abnormal transcripts, r.822_825del and [r.770U>C, r.652_771del, r.613_771del]. Six mutations, c.77G>A (p.R26H), c.517C>T (p.R173W), c.583C>T (p.R195C), c.673C>T (p.R225X), c.739T>C (p.C247R), and c.748G>C (p.E250A), have previously been identified in AIP patients from Western and other Eastern European populations. All mutations expressed in COS-1 cells demonstrated low residual activities (0.1-1%). The majority of the mutations were family-specific and also confirmed allelic heterogeneity among Russian AIP patients. The diversity of mutations may reflect the old international history of Saint Petersburg and immigration of people from other parts of Europe.

Clinical and biochemical characteristics and genotype-phenotype correlation in 143 Finnish and Russian patients with acute intermittent porphyria.

Acute intermittent porphyria (AIP), resulting from a deficiency of porphobilinogen deaminase (PBGD) in heme biosynthesis, is genetically heterogeneous and manifests with variable penetrance. The clinical outcome, prognosis, and correlation between PBGD genotype and phenotype were investigated in 143 Finnish and Russian AIP patients with 10 mutations (33G-->T, 97delA, InsAlu333, R149X, R167W, R173W, R173Q, R225G, R225X, 1073delA). Thirty-eight percent of the patients had experienced 1 or more acute attacks during their lives. The proportion of symptomatic patients has decreased dramatically from 49% to 17% among patients diagnosed before and after 1980, respectively. Patients with the R167W and R225G mutations showed lower penetrance (19% and 11%, respectively) and recurrence rate (33% and 0%, respectively) than patients with other mutations (range, 36%-67% and 0%-66%, respectively). Moreover, urinary excretions of porphyrins and their precursors were significantly lower in these patients (porphobilinogen [PBG], 47 +/- 10 vs. 163 +/- 21 micromol/L, p < 0.001; uroporphyrin, 130 +/- 40 vs. 942 +/- 183 nmol/d, p < 0.001). Erythrocyte PBGD activity did not correlate with PBG excretion in remission or with the clinical severity of the disease. Mutations R167W and R225G resulted in milder biochemical abnormalities and clinical symptoms indicating a milder form of AIP in these patients. In all AIP patients, normal PBG excretion predicted freedom from acute attacks. The risk of symptoms was highest for female patients with markedly increased PBG excretion (>100 micromol/L). Proper counseling contributed to the prevention of subsequent attacks in 60% of previously symptomatic and in 95% of previously symptom-free patients.