Variegate Porphyria

Variegate Porphyria

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Variegate Porphyria is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • VP
  • porphyria variegata

Disorder Subdivisions

  • None

General Discussion

Variegate porphyria is a rare genetic metabolic disorder characterized by deficient function of the enzyme protoporphyrinogen oxidase (PPO or PPOX). This deficiency is caused by heterozygous mutations in the PPOX gene, and leads to the accumulation of certain chemicals called porphyrins and porphyrin precursors in the body, which, in turn, can potentially result in a variety of symptoms. Specific symptoms can vary greatly from one person to another. Some affected individuals present with skin symptoms, some with neurological symptoms and some with both. Blistering and fragility of sun-exposed skin are the most common skin (cutaneous) symptoms. Common neurological symptoms include abdominal pain, nausea, vomiting, constipation, extremity pain and weakness, anxiety, restlessness and convulsions. Many different PPOX mutations have been identified in different families with variegate porphyria. The genetic mutation in a family is inherited as an autosomal dominant trait, but many individuals who inherit a PPOX mutation do not develop any symptoms (asymptomatic).



Variegate porphyria is one of a group of disorders known as the porphyrias. The porphyrias are characterized by abnormally high levels of porphyrins or porphyrin precursors in the body. Each porphyria is due to a deficiency of a different enzyme. There are eight enzymes in the pathway for making heme, which is a part of hemoglobin and other hemoproteins. There are at least eight types of porphyria. The symptoms associated with the various types of porphyria differ, depending upon the specific enzyme that is deficient. It is important to note that people who have one type of porphyria do not develop any of the other types. Porphyrias are generally classified into two groups: the "hepatic" and "erythropoietic" types. Porphyrins and porphyrin precursors originate in excess amounts from the liver in the hepatic types, and mostly from the bone marrow in the erythropoietic types. Variegate porphyria is a hepatic form of porphyria.



Protoporphyrinogen and coproporphyrinogen accumulate in the liver in variegate porphyria because PPOX is deficient, and become oxidized to protoporphyrin and coproporphyrin, which are transported in the blood plasma and cause the skin to be sensitive to sunlight. The neurological symptoms are associated with accumulation of porphyrin precursors, namely delta-aminolevulinic acid (ALA) and porphobilinogen (PBG).

Symptoms

The symptoms and severity of variegate porphyria can vary greatly from one person to another. Symptoms are rarely apparent before puberty. Affected individuals often develop skin (cutaneous) or neurological abnormalities or both. It is important to note that affected individuals may not have all of the symptoms discussed below. Affected individuals should talk to their physician about their specific case, associated symptoms and overall prognosis.



Many individuals with variegate porphyria may not develop any notable symptoms (asymptomatic) for all or most of their lives. Other individuals can develop a variety of symptoms. Cutaneous symptoms are chronic and commonly last for months or years. Neurological symptoms usually occur as acute attacks lasting days or weeks and occasionally become chronic. Acute attacks can be severe, and may occur in the absence of skin abnormalities.



Symptoms during an attack may include intense abdominal discomfort or pain, which is usually steady but may be cramping, nausea, vomiting, constipation (occasionally diarrhea) and trouble urinating. These symptoms are due to effects on the nerves of the bowel and bladder. The central nervous system is often affected with insomnia, restlessness, agitation, confusion, hallucinations and convulsions. The level of sodium in the blood may decrease and cause convulsions. The peripheral nerves are affected, leading to severe pain in the extremities, back or chest and, especially with more prolonged attacks, paralysis of muscles. This may progress to involve all extremities and the muscles that control breathing. The urine may be reddish due to increased porphyrins, and dark due to porphobilin, which is a brownish degradation product of PBG.



Increases in heart rate and blood pressure are very common on examination during attacks. Fever is usually absent or slight, because the neuropathy is not inflammatory. Reflexes may be increased initially and decreased or absent if motor neuropathy advances.



A variety of triggers are known to set off an acute attack. These include a variety of drugs, steroid hormones alcohol, decreased intake of calories or carbohydrates, and metabolic or possibly psychological stress. Women may have attacks during the second half of the menstrual cycle when progesterone levels are highest. In some cases, no trigger can be identified.



Chronic skin abnormalities result from photosensitivity, a condition in which the skin is abnormally sensitive to sunlight, causing blistering skin lesions. Symptoms include abnormally fragile skin, blisters (bullae), milia, which are tiny, white bumps or cysts, and excessive hair growth (hypertrichosis). Blisters are slow to heal and can scar leaving patches of skin that are abnormally dark (hyperpigmentation) or light (hypopigmentation). Skin symptoms may be less common in individuals who live in nontropical climates. Some individuals with variegate porphyria only develop skin abnormalities, others only develop neurological symptoms and some have both.



Individuals with variegate porphyria are at an increased risk for developing a form of liver cancer known as hepatocellular carcinoma. There is also risk of developing chronic kidney disease.

Causes

Variegate porphyria is caused by mutations of the PPOX gene. A PPOX mutation is inherited as an autosomal dominant trait within a family. The pattern of inheritance is autosomal dominant, which means that a single mutation is inherited from one parent and, in the presence of other triggering factors, is sufficient to cause the disease. The abnormal gene can be inherited from either parent, or on rare occasions can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.



The PPOX gene is located on the long arm (q) of chromosome 1 (1q22). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 1q22" refers to band 22 on the long arm of chromosome 1. The numbered bands specify the location of the thousands of genes that are present on each chromosome.



The PPOX gene contains instructions for creating PPOX, one of the eight enzymes necessary for the production of heme. Heme is an iron-containing porphyrin (iron protoporphyrin) and is a part of many heme-containing proteins (hemoproteins) in the body. Hemoproteins interact with oxygen and some are involved in electron transport and energy metabolism. The best known hemoprotein is hemoglobin, which is made in the bone marrow, makes red blood cells red, and transports oxygen from the lungs to other tissues. However, the bone marrow and hemoglobin are not affected in variegate porphyria. In this condition the heme pathway in the liver, which makes heme for other important hemoproteins, is affected.



Mutations of the PPOX gene result in deficient levels of PPOX, which, in turn, disrupts the biochemical process to create heme in the liver. This disruption causes porphyrins and porphyrin precursors to accumulate in the liver and these are then transported to other parts of the body to affect the nervous system and skin.



A variety of different triggers are known to lead to attacks in individuals with variegate porphyria. Many of these triggers act by increasing heme synthesis in the liver, which makes the PPOX deficiency more significant and increases the accumulation of porphyrins and porphyrin precursors. As noted above, triggers include a variety of drugs, hormones (especially progesterone), reduced intake of calories and carbohydrate, alcohol, and stress induced by infection or other illness.

Affected Populations

Some reports suggest that variegate porphyria affects more women than men. The incidence is estimated to occur in 1 in 100,000 individuals in the general population in European populations. The disorder occurs with the greatest frequency in South Africa in individuals of Dutch ancestry due to a founder effect. A founder effect is when a small isolated population of settlers (founders) expands over several generations leading to a high prevalence of a genetic trait. Most individuals with variegate porphyria in South Africa carry the same PPOX mutation and are descendents of a Dutch settler from the late 1600s. The incidence of variegate porphyria in South Africa among Caucasians is estimated to be 1 to 3 in 1,000 individuals.



Although, in most cases, the symptoms of variegate porphyria occur after puberty or later, very rare cases have been described where symptoms developed during infancy or childhood. Most such cases are homozygous cases who have inherited a PPOX mutation from each parent. Homozygous cases may have impaired mental development and photosensitivity, but acute attacks are not prominent.

Standard Therapies

Diagnosis

A diagnosis of variegate porphyria is suspected based upon symptoms and examination of the skin. None of the symptoms are specific, so the diagnosis must be confirmed by biochemical testing. In the evaluation of neurological symptoms, the other acute porphyrias need to be considered. For initial screening, a spot urine sample should be obtained for measurement of PBG, ALA and total porphyrins. If none of these is elevated, acute porphyrias can be excluded as a cause of recent or concurrent symptoms. PBG measurement is most important and specific for acute porphyrias. However PBG and ALA may be less elevated and return to normal more quickly after an attack of variegate porphyria (or hereditary coproporphyria) than in acute intermittent porphyria. Therefore, measurement of total urine porphyrins is important, keeping in mind that an elevation of urine porphyrins can occur in many other medical conditions.



When blistering skin manifestations are present, porphyria cutanea tarda, hereditary coproporphyria and even congenital erythropoietic porphyria are possibilities to differentiate. Measurement of plasma and fecal porphyrins and determining the wavelength of the fluorescence peak of plasma porphyrins is useful in differentiating these conditions.



Molecular genetic testing to identify a PPOX mutation is recommended for all biochemically confirmed cases of variegate porphyria. Molecular testing is sometimes useful when symptoms have been absent for months or years and biochemical abnormalities are no longer present. Knowing the PPOX mutation is a family enables other family members to be tested reliably for the same mutation.



Treatment

The treatment of acute attacks of variegate porphyria is the same as for acute intermittent porphyria and hereditary coproporphyria. Hospitalization is usually indicated for pain control and treatment of other severe symptoms such as nausea and vomiting, electrolyte imbalances and convulsions. Monitoring for these manifestations as well and muscle weakness and respiratory embarrassment is also indicated in severe attacks. A narcotic analgesic is generally required for pain, and a phenothiazine or ondansetron for nausea and vomiting. Triggering factors should be identified and discontinued when possible. The American Porphyria Foundation's website includes a database of safe and unsafe drugs (see Resources section of this report). Specific therapies are hemin for injection, which is available in the U.S. as lyophilized hematin (Panhematin®, Lundbeck), and glucose loading. Hemin represses the heme pathway in the liver and lowers ALA, PBG and porphyrins, and is associated with more rapid recovery from an attack. Glucose given intravenously has a similar effect, but because it is less potent is used only for mild attacks, or until hemin can be obtained from the manufacturer:



Lundbeck, Inc.

Four Parkway North

Deerfield, IL 60015

Website: www.lundbeckinc.com



Cimetidine has also been recommended based on little evidence, and should not be used as a substitute for hemin or even glucose. Acute attacks are potentially life-threatening especially if not treated promptly, but most patients recover completely. Future attacks can be prevented by avoiding triggering factors. Frequent attacks that are cyclic can be prevented by administration of a GnRH analogue. Frequent noncyclic attacks are rare, and can sometimes be prevented by prophylactic administration of hemin - perhaps a single dose weekly.



Chronic skin manifestations may improve if triggering factors are avoided. Hemin and glucose have not been found to be useful for this and other chronic symptoms. Treatments that are effective in porphyria cutanea tarda, namely phlebotomies and low-dose hydroxychloroquine or chloroquine, are not useful in variegate porphyria because, even though the skin abnormalities are the same, the underlying abnormalities in the liver are very different. Avoidance of exposure to sunlight is important and may lead to gradual improvement. The use of appropriate clothing (e.g., hats, long sleeved shirts) and opaque sunscreen products can be beneficial (regular sunscreen products are generally ineffective). More specific information on these preventive measures is available from the American Porphyria Foundation (see Resources section of this report).



Individuals with variegate porphyria should carry Medic Alert bracelets or wallet cards. Individuals may also carry a list of drugs that they need to avoid, but such lists may not be up to date and it is best to refer to the American Porphyria Foundation's website when needed. Genetic counseling may be of benefit for affected individuals and their families.

Investigational Therapies

At present, there are no treatment trials seeking patients with acute porphyrias. However, patients with any type of confirmed porphyria are sought by the Porphyrias Consortium for a Longitudinal Study to better define the natural history of these disorders. Updated information on clinical trials can be found at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Toll-free: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, in the main, contact:

www.centerwatch.com



For information about clinical trials conducted in Europe, contact:

https://www.clinicaltrialsregister.eu/



Study information is also posted at the Porphyrias Consortium website:

http://rarediseasesnetwork.epi.usf.edu/porphyrias/index.htm



Contact for additional information about variegate porphyria:



Karl E. Anderson, MD, FACP

University of Texas Medical Branch/UTMB Health

700 Harborside Drive

Galveston, TX 77555-1109

409-772-4661

409-772-6287 FAX

References

TEXTBOOKS

Phillips JD, Anderson KE. The porphyrias (Chapter 57). In: Kaushansky K, Lichtman MA, Beutler E, Kipps TJ, Seligson U, Prchal JT, eds. Williams Hematology, 8th edition. New York: McGraw-Hill 2010: 839-863.



Desnick RJ, Astrin KH, Anderson KE. Inherited porphyrias (Chapter 104). In: Rimoin DL, Conner JM, Pyeritz RE, Korf, BR, eds. Emery and Rimoin's Principles and Practice of Medical Genetics, 5th edition. Edinburgh: Churchill Livingston, 2007, pp 2331-2358.



JOURNAL ARTICLES

Anderson KE, Bloomer JR, Bonkovsky HL, Kushner JP, Pierach CA, Pimstone NR, Desnick RJ: Recommendations for the diagnosis and treatment of the acute porphyrias. Annals of Internal Medicine 2005;142:439-50.



Whatley SD, Mason NG, Woolf JR, et al. Diagnostic strategies for autosomal dominant acute porphyrias: retrospective analysis of 467 unrelated patients referred for mutational analysis of the HMBS, CPOX or PPOX gene. Clin Chem. 2009;55:1406-1414.



Whatley SD, Puy H, Morgan RR, et al. Variegate porphyria in Western Europe: identification of PPOX gene mutations in 104 families, extent of allelic heterogeneity, and absence of correlation between phenotype and type of mutation. Am J Hum Genet. 1999;65:984-994.



Kirsch RE, Meissner PN, Hift RJ. Variegate porphyria. Semin Liver Dis. 1998;18:33-41.



INTERNET

Poh-Fitzpatrick MB. Variegate Porphyria. Emedicine Journal, Sept. 1, 2011 Available at: http://emedicine.medscape.com/article/1103846-overview Accessed:February 21, 2013.



National Digestive Diseases Clearinghouse. Porphyria. April 30, 2012. Available at: http://digestive.niddk.nih.gov/ddiseases/pubs/porphyria/ Accessed:February 21, 2013.



Deybach JC. Porphyria Variegata. Orphanet encyclopedia. February 2009. Available at: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=79473 Accessed:February 21, 2013.



McKusick VA., ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:176200; Last Update:8/10/2010. Available at: http://www.ncbi.nlm.nih.gov/omim/176200 Accessed:February 21, 2013.

Resources

CLIMB (Children Living with Inherited Metabolic Diseases)

Climb Building

176 Nantwich Road

Crewe, CW2 6BG

United Kingdom

Tel: 4408452412173

Fax: 4408452412174

Email: enquiries@climb.org.uk

Internet: http://www.CLIMB.org.uk



American Porphyria Foundation

4900 Woodway, Suite 780

Houston, TX 77056-1837

Tel: (713)266-9617

Fax: (713)840-9552

Tel: (866)273-3635

Email: porphyrus@aol.com

Internet: http://www.porphyriafoundation.com



NIH/National Institute of Diabetes, Digestive & Kidney Diseases

Office of Communications & Public Liaison

Bldg 31, Rm 9A06

31 Center Drive, MSC 2560

Bethesda, MD 20892-2560

Tel: (301)496-3583

Email: NDDIC@info.niddk.nih.gov

Internet: http://www2.niddk.nih.gov/



MedicAlert Foundation International

2323 Colorado Avenue

Turlock, CA 95382

USA

Tel: (209)669-2401

Fax: (209)669-2456

Tel: (888)633-4298

Email: Inquiries@medicalert.org

Internet: http://www.medicalert.org



British Porphyria Association

136 Devonshire Rd

Durham City, DH1 2BL

United Kingdom

Tel: 01474369231

Email: helpline@porphyria.org.uk

Internet: http://www.porphyria.org.uk



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



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