Porphyria - symptoms and treatment

Porphyria - symptoms and treatment

Porphyria - The collective term for a group of eight inherited GENETIC DISORDERS of METABOLISM in which deficiencies of certain enzymes block the production of heme and allow the accumulation of porphyrins. Heme is an iron-containing pigment normally present in nearly all tissues in the body, notably as a component of HEMOGLOBIN in the BLOOD and of electron transport proteins called cytochromes. The LIVER produces cytochromes, which are essential for metabolizing numerous drugs, hormones, NUTRIENTS, and other substances. Heme synthesis occurs in a sequence of eight steps, each occurring through the actions of a particular enzyme. Each of the eight forms of porphyria represents the absence of one of these enzymes.

Symptoms of Porphyria and Diagnostic Path

Symptoms vary with the type of porphyria and may be neurologic (affect the NERVOUS SYSTEM), dermatologic (affect the SKIN), hepatic (involve the liver), or erythropoietic (involve the BONE MARROW and blood). Typically symptoms are episodic, occurring as attacks that last for days to weeks and sometimes longer. Symptoms vary widely in appearance, severity, and duration and may include

  • eruptive skin rashes (bullae)
  • PHOTOSENSITIVITY
  • severe ABDOMINAL PAIN
  • NAUSEA, VOMITING, and DIARRHEA
  • MUSCLE weakness and possibly PARALYSIS
  • agitation and hallucinations
  • tachycardia (rapid HEART RATE)
  • URINARY RETENTION and URINARY INCONTINENCE

The diagnostic path includes blood and urine tests to measure the presence of key porphyric enzymes. In people who know they have porphyria, exposure to identified precipitating factors —which include numerous drugs, hormones, and nutrients—will bring on an attack. HYPERTENSION (high BLOOD PRESSURE) can develop during an attack and persist after symptoms subside.

THE PORPHYRIAS
PorphyriaDeficient EnzymeInheritance Pattern
acute intermittent porphyria (AIP) porphobilinogen deaminase (PBG-D) autosomal dominant
ALAD-deficiency porphyria (ADP) aminolevulinic acid dehydratase (ALAD) autosomal recessive
congenital erythropoietic porphyria (CEP) uroporphyrinogen III cosynthase autosomal recessive
erythropoietic protoporphyria (EPP) ferrochelatase autosomal dominant
hepatoerythropoietic porphyria (HEP) uroporphyrinogen decarboxylase autosomal recessive
hereditary coproporphyria (HCP) coproporphyrinogen oxidase autosomal dominant
porphyria cutanea tarda (PCT) uroporphyrinogen decarboxylase autosomal dominant
variegate porphyria (VP) protoporphyrinogen oxidase autosomal dominant

Porphyria Treatment Options and Outlook

Severe symptoms, particularly neurologic, require hospitalization and aggressive treatment that may include intravenous heme administration (the only form in which heme is available). Medications safe to take to relieve and control symptoms include narcotic pain relievers and phenothiazines to relieve nausea and vomiting or neuropsychiatric symptoms. It is crucial to stop any substances that may have precipitated the attack. Most symptoms subside within two to three weeks, and most people fully recover within six weeks. Some people experience extended muscle weakness. Attacks may occur without provocation. Many people who have porphyria seldom experience attacks, however.

Risk Factors and Preventive Measures

The porphyrias are inherited genetic disorders. The risk of porphyria depends on the inheritance pattern. There are no measures to prevent porphyria. People who have porphyria, or who have family members who have porphyria, might consider GENETIC TESTING and GENETIC COUNSELING. It is possible to be a CARRIER for the autosomal recessive forms of porphyria.

See also BULLA; CYTOCHROME P450 (CYP450) ENZYMES; GENE; HALLUCINATION; HORMONE; MUTATION; RASH.

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Genetics and Molecular Medicine

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