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History and Epidemiology
Pseudoxanthoma elasticum is a rare genetic disorder with generalized degeneration of elastic fibers involving the skin, retina, cardiovascular, and gastrointestinal systems. In 1884, a French physician named Felix Balzer first described the disorder in a 49 year old man with pale yellow xanthomatous skin lesions present since childhood in flexural sites. The incidence of PXE is thought to be about 1 in 100,000, but is probably more common since many patients may remain undiagnosed. Both males and females appear equally involved, and are often diagnosed between the ages of 30 and 50, once multisystem complications have occurred. However, many patients report having had skin symptoms for a decade or more, often since childhood, prior to actual diagnosis. Pediatricians and family practitioners may not recognize these early dermatologic findings and diagnosis may be delayed until middle age, when other signs and symptoms occur. Case reports of patients diagnosed early on include both infants and young children. Skin lesions in childhood may be small and asymptomatic, and therefore overlooked. There is no strong sex or race predominance. Diagnosis is based upon the characteristic skin findings as well as skin biopsy revealing calcification and basophilic degeneration of the elastic tissue of the dermis.

Clinical Manifestations
The skin is the most obvious site of PXE involvement. Primary lesions are small, 1-5 mm. yellow-orange papules of varying shapes. They may coalesce into larger plaques that spread over mainly flexural areas of the body. The lateral neck is often the first site both involved and noticed. Case reports relate many children being teased for having a "dirty neck". Other areas of involvement include below the clavicles, axilla, antecubital and popliteal fossae, periumbilical area, perineum, and thighs. The face is typically spared, although mucous membranes may be involved. As dermatologic lesions progress, the skin may lose its elasticity and hang in lax folds. Cardiovascular, ophthalmologic, and gastrointestinal involvement cause the serious problems associated with PXE. These may rarely occur in childhood and usually are identified in adult patients. Eye changes include fibrotic angioid streaks, retinal hemorrhage, and central vision loss. Angioid streaks are gray to reddish-brown linear bands, caused by tears in Brush's membrane and resulting fibrosis. They are seen in 50-70 % of adult patients, but rarely in children. Pediatric patients may manifest an earlier lesion described as "peau d'orange" that may precede angioid streaks. Central vision loss is the most concerning disability that develops in adult patients with angioid streaks. Some of the retinal changes of PXE may be similar to findings in more common pediatric conditions, such as sickle cell disease, idiopathic thrombocytopenic purpura, Ehlers-Danlos Syndrome, and lead poisoning. Serious cardiovascular involvement includes coronary artery disease, peripheral artery disease with intermittent claudication and easy fatigability, mitral valve prolapse, and hypertension. Gastrointestinal complications may occur in younger patients. Gastric hemorrhage is one example that adolescents and, occasionally, pregnant women with PXE may experience. The stomach is the most common site. The bleeding is usually diffuse, not focal, and may be the presenting symptom of PXE. Medications which may cause gastric irritation should be avoided.

Genetics
PXE was initially believed to be a purely autosomal recessive condition. However, many families have been identified having pedigrees consistent with an autosomal dominant inheritance. Expression may be variable, and more than one type of genotype may actually exist. Researchers are working to identify the responsible gene. Candidates include the genes encoding elastin, the fibrillins, and lysyl oxidase. Careful family history and examination of all family members, including multiple generations, is essential. Genetic counseling should be provided to affected families.

Caring for the PXE Patient
No cure or specific therapy currently exists for PXE. Treatment goals include identifying affected family members, genetic counseling, and prevention of long-term multisystem sequelae. Once a child has been diagnosed with PXE, siblings, parents, and grandparents if possible should have careful dermatologic examinations to search for characteristic lesions. Include multiple generations if possible to assess the family's particular genetic pattern if possible. Genetic counseling should be provided to the parents and to any potentially sexually active teen patients. Many parents of newly diagnosed children may still be in their childbearing years. They must be informed that no prenatal diagnosis currently exists. Prevention of PXE complications is the focus of caring for the affected pediatric patient The major areas of concern are the eyes, cardiovascular and gastrointestinal systems, and nutrition. Obtain a baseline thorough ophthalmologic examination. Retinal hemorrhages rarely occur in children and adolescents, but are likely associated with mild to moderate head trauma. Discourage sports such as downhill skiing, in-line skating, football, and heavy weight lifting. Counsel about safety measures such as bicycle helmet use. Assessment of cardiovascular status should include measurement of blood pressure and pulses in all four extremities. Emphasize modifying those cardiac risk factors that can be controlled. Encourage regular exercise, appropriate weight for height, and abstinence from smoking. Cholesterol, HDL, and triglycerides should be measured and appropriate dietary interventions initiated when indicated. Gastrointestinal bleeding is one complication more likely to occur in younger patients. Advise avoidance of aspirin and non-steroidal medications such as ibuprofen which may promote gastric irritation. The latter medication is important to emphasize since its recent change in status to non-prescription has resulted in heavy advertising and ready availability for a variety of pediatric ailments. Instruct parents specifically on the common brand names for the over the counter NSAID's to avoid. Acetaminophen remains the safest medication for the pediatric patient who requires pain or fever control. Although it is recommended by some to restrict calcium, there is no evidence for this suggestion. Until proper studies are done, this remains an area of controversy.

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