Pseudoxanthoma Elasticum (PXE)

Pseudoxanthoma Elasticum (PXE)

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Pseudoxanthoma Elasticum (PXE) 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

  • Gronblad-Strandberg syndrome
  • elastosis dystrophica syndrome (obsolete)
  • systemic elastorrhexis (obsolete)

Disorder Subdivisions

  • None

General Discussion

Pseudoxanthoma elasticum, PXE, is an inherited disorder caused y mutations in the ABCC6 transporter gene that affects connective tissue in some parts of the body. Elastic tissue in the body becomes mineralized; that is, calcium and other minerals are deposited in the tissue. This can result in changes in the skin, eyes, cardiovascular system, and gastrointestinal system. Clinicians first recognized PXE more than 100 years ago. Researchers have made a number of significant advances in the past few years.

Symptoms

PXE results in a variety of signs and symptoms that vary in their number, type, and severity from person to person. Certain effects of PXE can cause serious medical problems, while others have less impact. Effects may include: skin changes, changes in the retina of the eye that may result in significant loss of central vision, changes in the cardiovascular system that may involve calcification of arteries and decreased blood flow in the arms and legs, and/or changes in the gastrointestinal system that may lead to bleeding in the stomach or intestines. At present, there is no way to predict the exact progression of the disorder for a particular individual. Some people have no skin lesions; others have no vision loss. Many people do not experience gastrointestinal complications or cardiovascular difficulties. A few have no manifestations of PXE except for a positive skin biopsy or angioid (resembling a blood vessel) streaks in the retina of the eye. The effects of PXE and its rate of progression seem to have no discernible pattern.



Skin: PXE often causes visible changes in the skin. These changes vary from person to person. The earliest changes tend to be in the skin on the sides of one's neck. Small lesions may develop. They may resemble a rash or have a "cobblestone" appearance. These lesions in the skin tend to progress slowly and unpredictably from the neck downward. Skin changes have often been reported in young children. The areas of the body that are most affected are those that bend and flex. The neck, the underarms, the skin on the inside of the elbows, the groin, and the skin behind the knees may be progressively affected, leading to loose folds in these areas. Lesions may appear on the inside of the lower lip or lining of the rectum or vagina. Some of these effects may be alleviated by reconstructive, or plastic, surgery.



It is possible to have PXE and not have any apparent skin lesions. In some individuals, careful examination of the skin by a dermatologist does not reveal any visible sign of lesions, but a positive biopsy indicates the diagnosis of PXE. Since the identification of mutations in the ABCC6 transporter gene as the cause of PXE, analysis of blood can be performed in research centers to confirm the presence or absence of mutations.



Eyes: PXE affects the retina of the eye. The first changes, visible only during an ophthalmologic examination, are called "peau d'orange" because the retina begins to resemble the skin of an orange. This does not affect vision and neither do characteristic irregular streaks, called angioid streaks that develop later. These streaks occur when mineralization of the highly elastic membrane behind the retina, called Bruch's membrane, leads to cracking. Small blood vessels beneath this layer take advantage of these breaks in the membrane and grow through the membrane. This is called neovascularization. Sometimes, these blood vessels leak and bleed. This bleeding results in the loss of central vision. While people with PXE may lose so much vision that they become legally blind, almost all people with PXE continue to have peripheral vision.



People who have PXE can use a tool called an Amsler grid to monitor their central vision. If there is swelling or bleeding in the center of the retina, this may cause the intersecting lines of the Amsler grid to appear distorted. A retinal specialist can instruct a patient in the use of an Amsler grid.



Cardiovascular system: Because PXE can cause mineralization and narrowing of blood vessels, affected individuals may experience cramping in the legs when they are walking, due to decreased blood flow. This decreased flow of blood is called intermittent claudication. Decreased flow of blood to the arms and legs may mean that one's pulse can no longer be felt in the wrists or feet. Some clinicians believe that hypertension (high blood pressure) and mitral valve prolapse may be more common among people with PXE than in the general population. However, these concerns have not been substantiated with large studies. Individuals with PXE should make periodic visits to their physician for monitoring of blood pressure, cholesterol, and pulses in the arms and legs. A heart-healthy lifestyle is recommended, with low-fat foods and plenty of exercise. Consistent exercise may decrease the effects of PXE on the blood vessels. Maintaining normal weight may also be beneficial. Smoking should be avoided.



Gastrointestinal system: Uncommonly, PXE may cause gastrointestinal bleeding. This is sometimes not recognized immediately and can be life-threatening. Little is known about the gastrointestinal effects of PXE, except that the bleeding is usually widespread in the stomach and/or intestines. In a few cases, this bleeding is mistaken for ulcers. A person with PXE experiencing any gastrointestinal difficulty should be sure to tell the attending physician that he or she has PXE. Some physicians recommend that affected individuals avoid non-steroidal, anti-inflammatory medications, such as aspirin, ibuprofen, and naproxen.



Pregnancy: It is thought that most women with PXE have normal pregnancies and that the incidence of pregnancy-related complications is similar to that of the general population. However, for some, gastric or intestinal complications have been reported. In general, complications affecting the fetus have not been reported. There are no prenatal tests to determine whether the fetus has PXE.

Causes

PXE is an inherited disorder. Most often PXE is inherited in a recessive pattern and has been attributed to mutations in the ABCC6 transporter gene.In recessive disorders, the condition does not occur unless an individual inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent. The risk is the same for each pregnancy.



In some instances, autosomal dominant inheritance has been reported in patients with PXE, but it is not clear if the dominant pattern is truly dominant or if it has been reported because, by chance, one parent is an asymptomatic heterozygote carrier of a mutated ABCC6 transporter gene while he second parent has the disorder. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy, regardless of the sex of the child. The risk is the same for each pregnancy.



Since PXE may be present but undiagnosed in other family members, it is recommended that all immediate relatives be screened for PXE by both an ophthalmologist and a dermatologist. The ophthalmologist should look for peau d'orange and angioid streaks. If suspicious for PXE, the dermatologist should take biopsies from the neck, under the arm and inside the elbow of a person suspected of having PXE. These biopsies may be necessary even if the skin doesn't show any visible lesions. Even with a negative biopsy, it is possible that other family members have PXE. PXE affects each individual with great variability. A blood test is available on a research basis to determine whether a person carries the gene.



The PXE gene has been identified. Known as ABC-C6, it is one of a group of genes that transport certain molecules back and forth across cell membranes. It isn't known at this time what molecules ABC-C6 transports, but it is thought that they may play a role in keeping the elastic fibers found in certain body tissues healthy.

Affected Populations

Estimates of the incidence of PXE range from 1 in 100,000 people to 1 in 25,000. However, the true incidence of PXE is not known in any population. It is likely that many individuals with PXE have not been diagnosed, particularly people with mild signs of PXE or those whose signs are not typical.

Standard Therapies

Diagnosis

Changes in the skin are usually the earliest sign of PXE and lead to the definitive diagnosis. Although the signs of PXE and the age of onset vary considerably, many people first notice an unusual appearance of their skin, typically on the sides or back of the neck. Small bumps, called lesions, may appear. Some individuals have described these as looking like a rash or an unwashed neck. Usually, a small biopsy of a lesion is done to confirm the diagnosis of PXE. This biopsy requires that a very small piece of skin, the size of a pencil eraser, be taken from the neck, underarm, and/or inside the elbow. The dermatologist sends this sample to a laboratory where a special stain, called a von Kossa stain, is used to detect calcium in the tissue.



Sometimes, changes in the eye are the first noticeable sign of PXE. Early changes in the eye are visible only during an ophthalmological examination. Later symptoms can include loss of central vision. Some people are first diagnosed with PXE when they notice distortion of their vision.



Treatment

A team of medical specialists (for example, an ophthalmologist, dermatologist, gastroenterologist, and primary care physician) may be needed to help manage PXE and its effects. People affected by PXE should be sure that all the health care professionals they visit are well-informed about the possible ramifications of PXE.



Regular physician exams by a knowledgeable primary care physician are necessary. A detailed family history should be taken with regard to onset, signs that may be related to PXE and the rest of the family's medical history. The affected individual's cholesterol and triglycerides should be checked. Peripheral pulses should be monitored, as well. A dermatologist will most likely be the physician to make the definitive diagnosis and offer advice on reconstructive surgery, if that is of interest to the patient. An ophthalmologist will dilate the eyes to look for peau d'orange and angioid streaks. If angioid streaks are found, it may be wise to consult a retinal specialist. A cardiologist can perform a baseline EKG and sonogram test.



In cases that involve retinal hemorrhage, laser treatment or injectible medications have been helpful for some people. However, not everyone can benefit from these treatments. In some cases, laser surgery does not restore vision. In others, scarring from both the bleeding and the laser surgery have made vision worse. A variety of visual aids can be provided to help compensate for loss of vision. A low vision clinic can be helpful in this regard.



It is generally thought that people affected by PXE should avoid activities that might cause direct trauma to the eyes. Activities that increase pressure in the eyes, such as weight lifting, should also be avoided.

Investigational Therapies

At this time, genetic research, including studies to characterize the gene mutations, is being conducted in several labs. Once the mutations have been identified, researchers will be able to study the changes that are caused by PXE and how to correct them or compensate for them.



Other PXE research includes clinical studies to determine what characterizes PXE, how it progresses, and what changes it causes in various systems of the body. In the next few years, it may be possible to determine, through a blood test, whether an individual has PXE.



Retinal research is advancing quickly. There are currently many projects looking at angioid streaks, retinal bleeding and what can be used to alleviate the bleeding and loss of vision that often follows.



Clinical research on PXE is currently being conducted at the following sites:



Lionel Bercovitch, M.D.

International PXE Registry, Epidemiological Study and Blood Bank

Genetic studies, mutational analysis, pathophysiology, MRI study

Department of Dermatology

Providence, RI 02912

Tel: 781-341-0530

E-mail: winnipegjet@earthlink.com



Mark Lebwohl, M.D.

PXE (Pseudoxanthoma Elasticum) Research Project

Department of Dermatology

Mount Sinai School of Medicine

Fifth Avenue & 100th Street

New York, NY 10029

Tel: 212-876-7199



Kenneth H. Neldner, M.D.

Pseudoxanthoma Elasticum (PSE) Research Program

Department of Dermatology

Health Sciences Center

Texas Tech University

Lubbock, TX 79430

Tel: 806-743-2456



Information on current clinical trials is posted on the Internet 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:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



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

www.centerwatch.com

References

TEXTBOOKS

Kanski JJ, ed. Clinical Ophthalmology, 4th ed. Woburn, MA: Butterworth-Heinemann; 1999:431-32.



Bennett JC, Plum F. eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:1123-24.



Yamada T, et al, eds. Textbook of Gastroenterology. 2nd ed. Philadelphia, PA: J.B. Lippincott Company; 1995:959-60.



Beighton P, ed. McKusick's Heritable Disorders of Connective Tissue. 5th ed. St. Louis, MO: Mosby-Year Book, Inc; 1993:335-65.



Kelley WN, et al, eds. Textbook of Rheumatology. 4th ed. Philadelphia, PA: W.B. Saunders Company; 1993:1585.



Champion RH, et al, eds. Textbook of Dermatology. 5th ed. Cambridge, MA: Blackwell Scientific Publications; 1992:1782-87, 2666.



Buyse ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:1425-6.



Habit, TP. Clinical Dermatology, 2nd ed. St. Louis, MO: C.V. Mosby Company; 1990: 659.



Gorlin RJ, et al, eds. Syndromes of the Head and Neck, 3rd ed. New York, NY: Oxford University Press; 1990:478-81.



Braunwald E, ed. Heart Disease. A Textbook of Cardiovascular Medicine. 3rd ed. Philadelphia, PA: W. B. Saunders Company; 1988:1728.



JOURNAL ARTICLES

Ringpfeil F, et al. Pseudoxanthoma elasticum: mutations in the MRP6 gene encoding a transmembrane ATP-binding cassette (ABC) transporter. Proc Natl Acad Sci USA. 2000;97:6001-6.



Le Saux O, et al. Mutations in a gene encoding an ABC transporter cause pseudoxanthoma elasticum. Nat Genet. 2000;25:223-7.



Bergen AA, et al. Mutations in the ABCC6 gene cause pseudoxanthoma elasticum. Nat Genet. 2000;25:228-31.



Bale SJ, et al. Recent advances in gene mapping of skin diseases. Pseudoxanthoma elasticum: a satisfying sibling study. J Cutan Med Surg. 1999;3:154-6.



Uitto J, et al. Report on the international centennial meeting on pseudoxanthoma elasticum. J Investigative Dermatology. 1998;110:840-2.



Van Soest S, et al. A locus for autosomal recessive pseudoxanthoma elasticum, with penetrance of vascular symptoms in carriers, maps to chromosome 16p13.1. Genome Research. 1997;7:830-84.



Struk B, et al. Mapping of both autosomal recessive and dominant variants of pseudoxanthoma elasticum to chromosome 16p13.1. Human Molecular Genetics. 1997;6:1823-28.



Truter S, et al. Calcification of elastic fibers in pseudoxanthoma elasticum. Mt Sinai J Med. 1996;63:210-5.



Godrey M, et al. Fibrillin immunofluorescence in pseudoxanthoma elasticum. J Am Acad Dermatol. 1995;32:589-94.



INTERNET

Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Pseudoxanthoma Elasticum; PXE. Entry No: 264800. Last Updated February 8, 2012.

Available at: http://www.ncbi.nlm.nih.gov/omim/. Accessed February 15, 2012.



Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. http://omim.org/geneMap/16/154?start=-3&limit=10&highlight=154Pseudoxanthoma Elasticum, Forme Fruste. Entry No: 177850. Last Edited June 29, 2010. Available at: http://www.ncbi.nlm.nih.gov/omim/. Accessed February 15, 2012.

Resources

National Association for Pseudoxanthoma Elasticum

8760 Manchester Road

St. Louis, MO 63144-2724

USA

Tel: (314)962-0100

Fax: (314)962-0100

Email: NAPEStLouis@sbcglobal.net

Internet: http://www.pxenape.org/



NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

Information Clearinghouse

One AMS Circle

Bethesda, MD 20892-3675

USA

Tel: (301)495-4484

Fax: (301)718-6366

Tel: (877)226-4267

TDD: (301)565-2966

Email: NIAMSinfo@mail.nih.gov

Internet: http://www.niams.nih.gov/



NIH/National Eye Institute

31 Center Dr

MSC 2510

Bethesda, MD 20892-2510

United States

Tel: (301)496-5248

Fax: (301)402-1065

Email: 2020@nei.nih.gov

Internet: http://www.nei.nih.gov/



NIH/National Heart, Lung and Blood Institute

P.O. Box 30105

Bethesda, MD 20892-0105

Tel: (301)592-8573

Fax: (301)251-1223

Email: nhlbiinfo@rover.nhlbi.nih.gov

Internet: http://www.nhlbi.nih.gov/



Coalition for Heritable Disorders of Connective Tissue (CHDCT)

4301 Connecticut Avenue, NW Suite 404

Washington, DC 20008

Tel: (202)362-9599

Fax: (202)966-8553

Tel: (800)778-7171

Email: chdct@pxe.org

Internet: http://www.chdct2.org/



PXE International, Inc.

4301 Connecticut Ave NW

Suite 404

Washington, DC 20008-2304

USA

Tel: (202)362-9599

Fax: (202)966-8553

Email: info@pxe.org

Internet: http://www.pxe.org



MD Support - The Eyes of the Macular Degeneration Community

3600 Blue Ridge Blvd

Grandview, MO 64030

USA

Tel: (816)761-7080

Fax: (816)761-7080

Email: director@mdsupport.org

Internet: http://www.mdsupport.org



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/



Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org



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