Current and innovative emerging therapies for porphyrias with hepatic involvement.

Porphyrias are rare inherited disorders caused by specific enzyme dysfunctions in the haem synthesis pathway, which result in abnormal accumulation of specific pathway intermediates. The symptoms depend upon the chemical characteristics of these substances. Porphyrins are photoreactive and cause photocutaneous lesions on sunlight-exposed areas, whereas accumulation of porphyrin precursors is related to acute neurovisceral attacks. Current therapies are suboptimal and mostly address symptoms rather than underlying disease mechanisms. Advances in the understanding of the molecular bases and pathogenesis of porphyrias have paved the way for the development of new therapeutic strategies. In this Clinical Trial Watch we summarise the basic principles of these emerging approaches and what is currently known about their application to porphyrias of hepatic origin or with hepatic involvement.

Pathogenesis and clinical features of the acute hepatic porphyrias (AHPs).

The acute hepatic porphyrias include four disorders: acute intermittent porphyria [AIP], hereditary coproporphyria [HCP], variegate porphyria [VP], and the rare porphyria due to severe deficiency of ALA dehydratase [ADP]. In the USA, AIP is the most severe and most often symptomatic. AIP, HCP, and VP are due to autosomal dominant genetic abnormalities, in which missense, nonsense, or other mutations of genes of normal hepatic heme biosynthesis, in concert with other environmental, nutritional, hormonal and genetic factors, may lead to a critical deficiency of heme, the end-product of the pathway, in a small but critical 'regulatory pool' within hepatocytes. This deficiency leads to de-repression of the first and normally rate-controlling enzyme of the heme synthetic pathway, delta- or 5-aminolevulinic acid [ALA] synthase-1, and thus to marked up-regulation of this key enzyme and to marked hepatic overproduction of ALA. In addition, except for ADP, there is marked overproduction as well of porphobilinogen [PBG], the intermediate immediately downstream of ALA in the synthetic chain, and, especially in HCP and VP, also porphyrinogens and porphyrins farther down the pathway. The major clinical features of the acute porphyrias are attacks of severe neuropathic-type pain. Pain is felt first and foremost in the abdomen but may also occur in the back, chest, and extremities. Attacks are more common in women than in men [ratio of about 4:1], often accompanied by nausea, vomiting, constipation, tachycardia, and arterial hypertension. Hyponatremia may also occur. Some patients also describe chronic symptoms of pain, anxiety, insomnia, and others.

Hepatic porphyria: A narrative review.

Porphyrias are a group of metabolic disorders, which result from a specific abnormality in one of the eight enzymes of the heme biosynthetic pathway. These have been subdivided based on the predominant site of enzyme defect into hepatic and erythropoietic types and based on clinical presentation into acute neurovisceral and cutaneous blistering porphyrias. This review focuses on hepatic porphyrias, which include acute intermittent porphyria (AIP), variegate porphyria (VP), hereditary coproporphyria (HCP), aminolevulinic acid dehydratase deficiency porphyria (ADP), and porphyria cutanea tarda (PCT). Of these, AIP and ADP are classified as acute porphyria, PCT as cutaneous, while VP and HCP present with both acute and cutaneous clinical manifestations. Porphobilinogen levels in a spot urine sample is the initial screening test for the diagnosis of acute hepatic porphyria, and plasma with spot urine porphyrin levels is the initial screening test to approach patients suspected of cutaneous porphyria. Specific biochemical porphyrin profile for each porphyria helps in determining the specific diagnosis. Pain relief and elimination of triggering agents are the initial steps in managing a patient presenting with an acute attack. Intravenous glucose administration terminates the mild episode of acute porphyria, with intravenous hemin needed for management of moderate to severe episodes. Liver transplantation is curative and may be needed for patients with a life-threatening acute porphyria attack or for patients with recurrent acute attacks refractory to prophylactic treatment. Of the cutaneous porphyrias, PCT is the most common and is frequently associated with a combination of multiple susceptibility factors such as alcohol use, smoking, hepatitis C virus infection, HIV infection, estrogen use, and mutations of the hemochromatosis gene. Regular phlebotomy schedule and low-dose hydroxychloroquine are effective and safe treatment options for management of PCT.

The acute hepatic porphyrias: current status and future challenges.

The porphyrias are predominantly inherited metabolic disorders, which result from a specific deficiency of one of the eight enzymes along the pathway of haem biosynthesis. Historically, they have been classified into hepatic and erythropoietic forms, based on the primary site of expression of the prevailing dysfunctional enzyme. From a clinical point of view, however, it is more convenient to subdivide them into acute and non-acute porphyrias, thereby primarily considering the potential occurrence of life-threatening acute neurovisceral attacks. Unrecognised or untreated, such an acute porphyric attack is associated with a significant mortality of up to 10%. The acute hepatic porphyrias comprise acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase deficiency porphyria. Making a precise diagnosis may be difficult because the different types of porphyrias may show overlapping clinical and biochemical characteristics. To date, the therapeutic possibilities are limited and mainly symptomatic. In this overview we report on what is currently known about pathogenesis, clinic, diagnostics, and therapy of the acute hepatic porphyrias. We further point out actual and future challenges in the management of these diseases.

Porphyric neuropathy.

The hepatic porphyrias are a group of rare metabolic disorders characterized by enzymatic defects in the biosynthesis of heme, a metalloporphyrin that is the principal product of porphyrin metabolism. The hepatic porphyrias are genetically transmitted as autosomal-dominant disorders with variable expression that produce a particularly severe form of neuropathy. Most medical students readily recognize acute attacks of porphyria when the classic triad of abdominal pain, psychosis, and neuropathy is present. Yet, porphyric neuropathy is a source of confusion in practice, and patients with porphyria rarely receive the correct diagnosis early in the course of the illness. Porphyric neuropathy is manifest by symptoms, signs, and cerebrospinal fluid abnormalities resembling acute Guillain-Barré syndrome. However, accompanying psychological features, a proximal predilection of asymmetric weakness, and electrodiagnostic findings indicative of an axonal polyradiculopathy or neuronopathy all suggest the diagnosis of porphyria. Confirmation of the diagnosis depends on use of appropriate laboratory studies. The underlying pathophysiology of porphyric neuropathy has not been established, but it may be related to direct neurotoxicity of elevated levels of delta-aminolevulinic acid. The severity of the neuropathy and the availability of potential treatments, including avoidance of provocative factors, make identification important.

Porfiria cutánea tarda, con infiltraciones calcáreas / Porphyria cutanea tarda with calcium infiltration

La porfiria cutánea tarda es un desorden del metabolismo del hemo, caracterizado por un aumento de porfirinas y porfinuria, como consecuencia de la disminución en la actividad enzimática uroporfirinógeno decarboxilasa. El signo clínico más importante es la fotosensibilidad cutánea. Este traabajo se realiza a propósito de un caso de porfiria tarda con infiltraciones calcáreas, una revisión de la porfiria cutánea tarda como entidad clínica, considerándose en particular su variante esporádica (AU)

Porfiria cutánea tarda, con infiltraciones calcáreas / Porphyria cutanea tarda with calcium infiltration

La porfiria cutánea tarda es un desorden del metabolismo del hemo, caracterizado por un aumento de porfirinas y porfinuria, como consecuencia de la disminución en la actividad enzimática uroporfirinógeno decarboxilasa. El signo clínico más importante es la fotosensibilidad cutánea. Este traabajo se realiza a propósito de un caso de porfiria tarda con infiltraciones calcáreas, una revisión de la porfiria cutánea tarda como entidad clínica, considerándose en particular su variante esporádica

Human hereditary hepatic porphyrias.

The human hereditary hepatic porphyrias are diseases due to marked deficiencies of enzymes in the heme biosynthetic pathway. Porphyrias can be classified as either hepatic or erythroid, depending on the major production site of porphyrins or their precursors. The pathogenesis of inherited hepatic porphyrias has now been defined at the molecular level. Some gene carriers are vulnerable to a range of exogenous and endogenous factors, which may trigger neuropsychiatric and/or cutaneous symptoms. Early diagnosis is of prime importance since it makes way for counselling. In this article we present an overview of recent advances on hepatic porphyrias: 5-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria (AIP), porphyria cutanea tarda (PCT), hereditary coproporphyria (HC), and variegate porphyria (VP).

[The hepatic porphyrias: experience with 105 cases]. / Las porfirias hepáticas: experiencia con 105 casos.

Hepatic porphyria is a rare metabolic syndrome caused by abnormal enzyme activity in heme biosynthesis. Between 1974 and 1991; 105 patients have met criteria for diagnosis of hepatic porphyria based on typical clinical findings and/or laboratory abnormalities. According to type, 42% had porphyria cutanea tarda, 21% porphyria variegate, 15% protoporphyria, 6.7% acute intermittent porphyria, 6.7% coproporphyria and 1.9% porphyria due to porphobilinogen deficit. A proper classification was not established in 6.7% of patients. Porphyria cutanea tarda was more common in males (70%) and porphyria variegata, in females (90%). A family history of the disease was present in 33% of patients; 20% of patients were of European descent and 4% of Mapuche descent. Diagnosis was usually established in the third decade, somewhat later in porphyria cutanea tarda (45 years of age) and very early in protoporphyria. 10% of patients were asymptomatic and 29 patients developed at least one porphyric crisis. These were related to pregnancy in 6 patients, to hormone administration in 7, to antibiotics in 5. No cause was established in 21 cases. Severe crisis were successfully treated with Hematin. Venipuncture was used to treat 50% of patients with porphyria cutanea tarda with 95% success. Thus, hepatic porphyria is recognized with increasing frequency and can be treated successfully in most cases.