Pseudoxanthoma Elasticum (PXE) is an inherited disorder in which elastic fibres, which are normally found in the skin, the retina of the eyes and the cardiovascular system become slowly calcified, producing characteristic changes in these three areas. It is estimated that about 1 in 70,000 people in the world has PXE and for no known reason the condition affects twice as many females as males. The average age of onset is about 13 years with a range from 2 to 20 years. The cause of the disease is unknown.
The first manifestation, and the one which nearly always makes the diagnosis possible, is the appearance of highly characteristic, slightly thickened, patches of skin. The skin changes seen in PXE are variable. Some individuals experience very little change, whilst in others the small 2-5 mm yellowish or yellow-orange papules may form groups or coalesce into larger plaques giving a cobblestone or plucked chicken appearance. The skin may become lax or folded. The appearance and location of skin lesions can cause psychological distress. They most commonly first appear on the sides of the neck, which leads to younger persons being accused of not having washed properly.
Lesions later appear in other flexural areas, for example under the arms, folds of the arms, the groin and behind the knees. The diagnosis can be confirmed by a skin biopsy, a procedure in which a small piece of skin is removed for analysis. In PXE, the biopsy will show a distinctive calcification of the elastic fibres.
Widespread involvement of the body is rare. In some cases the onset of skin lesions may be delayed until late in life, but many such individuals probably had small skin lesions for many years which were unrecognised as PXE. In a few individuals, suspected of having PXE, the skin involvement is so mild it may be thought to be lacking, but very careful examination, or a skin biopsy, will confirm a diagnosis.
Involvement of other systems: As has already been mentioned, the effects of PXE can go far beyond those affecting the skin, which are the most characteristic effects of PXE. The ocular and cardiovascular manifestations are responsible for the morbidity of the disease. The eyes of 60% of those with PXE will be affected eventually, usually in middle life. A smaller number will suffer from cardiovascular problems affecting the heart and legs (intermittent claudication), and from gastrointestinal bleeding.
Skin lesions are asymptomatic, causing no medical problems in themselves, but can be cosmetically objectionable if they become severe. There is no specific treatment to change the appearance of the skin lesions and skin folds, other than plastic surgery. Good cosmetic results have been achieved on the neck, however plastic surgery on the axillae is more difficult. Some improvement is possible if the skin sags excessively in these areas.
Attention to a proper, balanced diet and control of calcium intake will help slow down the process which affects the skin. Calcium is needed for life and a normal physiology, but not in excessive amounts. A calcium intake of no more than 800mg per day is recommended. If necessary a dietitian should be consulted to help maintain a balanced diet.
The current research in all hereditary disorders is to look for the defective gene responsible for the condition and then attempt to add or replace the missing or altered substance. In May 2000, the good news that the PXE gene had been isolated was sent round the world. The gene has been identified as 'ABC-C6'. Researchers are now addressing the question of how and why a loss of function of the ABC-6 leads to PXE. The answer to this will hold important clues towards treating and/or preventing the illness.
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