Inborn Errors of Metabolism: Pseudoxanthoma Elasticum.

Pseudoxanthoma elasticum (PXE) is an autosomal recessive multisystem disorder that involves the skin, GI tract, and heart, as well as the eye. It affects approximately 1 in 50,000 people worldwide and is seen twice as frequently in females as in males. Fundus findings include angioid streaks (Fig. 38.1), reticular macular dystrophy, speckled appearance temporal to the macula (peau d'orange, like the dimpled texture of an orange peel), drusen of the optic nerve, and vitelliform-like deposits. Peau d'orange may precede the development of an angioid streak. "Comets," with or without a tail, are seen as solitary subretinal, nodular white bodies of retinal pigment epithelium (RPE) atrophy, usually present in the mid periphery (Fig. 38.2). The tail points toward the optic disc. Patients sometimes develop choroidal neovascular membrane. Skin changes (plucked chicken-like appearance) occur on the flexure areas, including the neck and axilla, as well as increased skin laxity with excessive skin folding. Cardiovascular changes include accelerated atherosclerosis with occlusive vascular disease leading to angina, hypertension, restrictive cardiomyopathy, mitral valve prolapse, and others. Progressive calcification and fragmentation of elastic fibers in the skin, eye, and cardiovascular system is the underlying pathophysiology.