Porphyria

Porphyria is a group of diseases in which substances called porphyrins build up, negatively affecting the skin or nervous system. The types that affect the nervous system are also known as acute porphyria, as symptoms are rapid in onset and last a short time. Symptoms of an attack include abdominal pain, chest pain, vomiting, confusion, constipation, fever, high blood pressure, and high heart rate. The attacks usually last for days to weeks. Complications may include paralysis, low blood sodium levels, and seizures. Attacks may be triggered by alcohol, smoking, hormonal changes, fasting, stress, or certain medications. If the skin is affected, blisters or itching may occur with sunlight exposure. Most types of porphyria are inherited from one or both of a person's parents, and are due to a mutation in one of the genes that make heme. They may be inherited in an autosomal dominant, autosomal recessive, or X-linked dominant manner. One type, porphyria cutanea tarda, may also be due to increased iron in the liver, hepatitis C, alcohol, or HIV/AIDS. The underlying mechanism results in a decrease in the amount of heme produced and a build-up of substances involved in making heme. Porphyrias may also be classified by whether the liver or the bone marrow is affected. Diagnosis is typically made by blood, urine, and stool tests. Genetic testing may be done to determine the specific mutation. Treatment depends on the type of porphyria and a person's symptoms. The treatment of porphyria of the skin generally involves the avoidance of sunlight. The treatment for acute porphyria may involve giving intravenous heme or a glucose solution. Rarely a liver transplant may be carried out. The precise frequency of porphyria is unclear: it is estimated that it affects somewhere between 1 and 100 per 50,000 people. Rates vary around the world. Porphyria cutanea tarda is believed to be the most common type. The disease was described as early as 370 BC by Hippocrates. The underlying mechanism was first described by Felix Hoppe-Seyler in 1871. The name porphyria is from the Greek πορφύρα, porphyra, meaning 'purple', a reference to the color of the urine that may occur during an attack. The acute porphyrias are acute intermittent porphyria (AIP), variegate porphyria (VP), aminolevulinic acid dehydratase deficiency porphyria (ALAD) and hereditary coproporphyria (HCP). These diseases primarily affect the nervous system, resulting in episodic crises known as acute attacks. The major symptom of an acute attack is abdominal pain, often accompanied by vomiting, hypertension (elevated blood pressure), and tachycardia (an abnormally rapid heart rate). The most severe episodes may involve neurological complications: typically motor neuropathy (severe dysfunction of the peripheral nerves that innervate muscle), which leads to muscle weakness and potentially to quadriplegia (paralysis of all four limbs) and central nervous system symptoms such as seizures and coma. Occasionally, there may be short-lived psychiatric symptoms such as anxiety, confusion, hallucinations, and, very rarely, overt psychosis. All these symptoms resolve once the acute attack passes. Given the many presentations and the relatively low occurrence of porphyria, patients may initially be suspected to have other, unrelated conditions. For instance, the polyneuropathy of acute porphyria may be mistaken for Guillain–Barré syndrome, and porphyria testing is commonly recommended in those situations. The non-acute porphyrias are X-linked dominant protoporphyria (XLDPP), congenital erythropoietic porphyria (CEP), porphyria cutanea tarda (PCT), and erythropoietic protoporphyria (EPP). None of these are associated with acute attacks; their primary manifestation is with skin disease. For this reason, these four porphyrias—along with two acute porphyrias, VP and HCP, that may also involve skin manifestations—are sometimes called cutaneous porphyrias.