Classification & external resources
|| E80.2 (ILDS E80.230)
Variegate porphyria is a subtype of porphyria that can have acute (severe but usually not long-lasting) symptoms along with symptoms that affect the skin. The disorder results from low levels of the enzyme responsible for the seventh step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood.
Many people with this disorder never experience symptoms. When symptoms occur, they can include acute attacks (similar to acute intermittent porphyria), skin damage, or both. Acute attacks usually begin in adulthood and cause abdominal pain, vomiting, diarrhea and constipation. During an attack, a person may also experience muscle weakness, seizures, and mental changes such as anxiety and hallucinations. These signs and symptoms are triggered by nongenetic factors such as certain drugs, dieting or fasting, certain hormones and stress.
Some people with variegate porphyria have skin that is overly sensitive to sunlight. Areas of skin exposed to the sun develop severe blistering, scarring, changes in pigmentation, and increased hair growth. Exposed skin becomes fragile and is easily damaged.
Rarely, the signs and symptoms of variegate porphyria can begin in infancy or early childhood. In such cases, the signs and symptoms are usually more severe than those starting later in life. In addition to the health problems described above, children with this disorder may have mental retardation and grow more slowly than other children.
This type of porphyria is most common in the white population of South Africa; about 3 per 1,000 people in this population are diagnosed each year. The disorder occurs much less frequently in other parts of the world.
Mutations in the PPOX gene cause variegate porphyria. The PPOX gene makes a membrane bound mitochondrial enzyme called protoporphyrinogen oxidase, which is critical to the chemical process that leads to heme production. The activity of this enzyme is reduced by 50 percent in most people with variegate porphyria. In severe cases that begin early in life, the enzyme is almost completely inactive. Nongenetic factors such as certain drugs, stress, and others listed above can increase the demand for heme and the enzymes required to make heme. The combination of this increased demand and reduced activity of protoporphyrinogen oxidase disrupts heme production and allows byproducts of the process to accumulate in the liver, triggering an acute attack.
Variegate porphyria is inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to decrease enzyme activity and cause symptoms. More severe cases result from inheriting two copies of the altered gene.
The entire PPOX gene has about 8kb with 13 exon sequences. It was successfully cloned from a cDNA library in 1995 revealing that, after processing, it is 477 nucleotides long. It has previously been thought that the PPOX gene was located on human chromosome 14, however mapping experiments (FISH) have shown that it is near 1q22. An additional aggravating mutation affecting variegate porphyria can be found at 6p21.3 on the HFE gene.
- Anderson KE, Bloomer JR, Bonkovsky HL, Kushner JP, Pierach CA, Pimstone NR, Desnick RJ (2005). "Recommendations for the diagnosis and treatment of the acute porphyrias". Ann Intern Med 142 (6): 439-50. PMID 15767622.
- Chemmanur AT, Bonkovsky HL (2004). "Hepatic porphyrias: diagnosis and management". Clin Liver Dis 8 (4): 807-38, viii. PMID 15464657.
- Hift RJ, Meissner D, Meissner PN (2004). "A systematic study of the clinical and biochemical expression of variegate porphyria in a large South African family". Br J Dermatol 151 (2): 465-71. PMID 15327556.
- Hift RJ, Meissner PN (2005). "An analysis of 112 acute porphyric attacks in Cape Town, South Africa: Evidence that acute intermittent porphyria and variegate porphyria differ in susceptibility and severity". Medicine (Baltimore) 84 (1): 48-60. PMID 15643299.
- Kauppinen R (2005). "Porphyrias". Lancet 365 (9455): 241-52. PMID 15652607.
- Lecha M, Herrero C, Ozalla D (2003). "Diagnosis and treatment of the hepatic porphyrias". Dermatol Ther 16 (1): 65-72. PMID 12919129.
- Nordmann Y, Puy H (2002). "Human hereditary hepatic porphyrias". Clin Chim Acta 325 (1-2): 17-37. PMID 12367763.
- Sassa S (2002). "The porphyrias". Photodermatol Photoimmunol Photomed 18 (2): 56-67. PMID 12147038.
This article incorporates public domain text from The U.S. National Library of Medicine
|Metabolic pathology / Inborn error of metabolism (E70-90, 270-279)|
|Amino acid||Aromatic (Phenylketonuria, Alkaptonuria, Ochronosis, Tyrosinemia, Albinism, Histidinemia) - Organic acidemias (Maple syrup urine disease, Propionic acidemia, Methylmalonic acidemia, Isovaleric acidemia, 3-Methylcrotonyl-CoA carboxylase deficiency) - Transport (Cystinuria, Cystinosis, Hartnup disease, Fanconi syndrome, Oculocerebrorenal syndrome) - Sulfur (Homocystinuria, Cystathioninuria) - Urea cycle disorder (N-Acetylglutamate synthase deficiency, Carbamoyl phosphate synthetase I deficiency, Ornithine transcarbamylase deficiency, Citrullinemia, Argininosuccinic aciduria, Hyperammonemia) - Glutaric acidemia type 1 - Hyperprolinemia - Sarcosinemia|
|Carbohydrate||Lactose intolerance - Glycogen storage disease (type I, type II, type III, type IV, type V, type VI, type VII) - fructose metabolism (Fructose intolerance, Fructose bisphosphatase deficiency, Essential fructosuria) - galactose metabolism (Galactosemia, Galactose-1-phosphate uridylyltransferase galactosemia, Galactokinase deficiency) - other intestinal carbohydrate absorption (Glucose-galactose malabsorption, Sucrose intolerance) - pyruvate metabolism and gluconeogenesis (PCD, PDHA) -
Pentosuria - Renal glycosuria|
|Lipid storage||Sphingolipidoses/Gangliosidoses: GM2 gangliosidoses (Sandhoff disease, Tay-Sachs disease) - GM1 gangliosidoses - Mucolipidosis type IV - Gaucher's disease - Niemann-Pick disease - Farber disease - Fabry's disease - Metachromatic leukodystrophy - Krabbe disease|
Neuronal ceroid lipofuscinosis (Batten disease) - Cerebrotendineous xanthomatosis - Cholesteryl ester storage disease (Wolman disease)
|Fatty acid metabolism||Lipoprotein/lipidemias: Hyperlipidemia - Hypercholesterolemia - Familial hypercholesterolemia - Xanthoma - Combined hyperlipidemia - Lecithin cholesterol acyltransferase deficiency - Tangier disease - Abetalipoproteinemia |
Fatty acid: Adrenoleukodystrophy - Acyl-coA dehydrogenase (Short-chain, Medium-chain, Long-chain 3-hydroxy, Very long-chain) - Carnitine (Primary, I, II)
|Mineral||Cu Wilson's disease/Menkes disease - Fe Haemochromatosis - Zn Acrodermatitis enteropathica - PO43�' Hypophosphatemia/Hypophosphatasia - Mg2+ Hypermagnesemia/Hypomagnesemia - Ca2+ Hypercalcaemia/Hypocalcaemia/Disorders of calcium metabolism|
and acid-base balance
|Electrolyte disturbance - Na+ Hypernatremia/Hyponatremia - Acidosis (Metabolic, Respiratory, Lactic) - Alkalosis (Metabolic, Respiratory) - Mixed disorder of acid-base balance - H2O Dehydration/Hypervolemia - K+ Hypokalemia/Hyperkalemia - Cl�' Hyperchloremia/Hypochloremia|
|Purine and pyrimidine||Hyperuricemia - Lesch-Nyhan syndrome - Xanthinuria|
|Porphyrin||Acute intermittent, Gunther's, Cutanea tarda, Erythropoietic, Hepatoerythropoietic, Hereditary copro-, Variegate|
|Bilirubin||Unconjugated (Lucey-Driscoll syndrome, Gilbert's syndrome, Crigler-Najjar syndrome) - Conjugated (Dubin-Johnson syndrome, Rotor syndrome)|
|Glycosaminoglycan||Mucopolysaccharidosis - 1:Hurler/Hunter - 3:Sanfilippo - 4:Morquio - 6:Maroteaux-Lamy - 7:Sly|
|Glycoprotein||Mucolipidosis - I-cell disease - Pseudo-Hurler polydystrophy - Aspartylglucosaminuria - Fucosidosis - Alpha-mannosidosis - Sialidosis|
|Other||Alpha 1-antitrypsin deficiency - Cystic fibrosis - Amyloidosis (Familial Mediterranean fever) - Acatalasia|