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A 50 year old woman with progressive dimness of vision was referred by ophthalmologists for evaluation of her skin lesions. She had asymptomatic, yellowish, papular lesions on the sides and front of her neck, axillae, and periumbilical region. The lesions had been present since puberty and non-progressive for the past several years. She was hypertensive on irregular treatment. She had two uneventful pregnancies and the children were normal. Her mother and elder sister had similar skin lesions of long duration.
On examination, her peripheral pulses were normal. Supine blood pressure was 150/100 mm Hg. The skin in the involved areas was lax and redundant with yellowish, waxy, papular lesions giving rise to a cobblestone appearance (fig 1). The inner aspect of her lips and buccal mucosa showed a yellowish pebbled surface. Ophthalmoscopy revealed bilateral choroiditis. With the above features, a clinical diagnosis of pseudoxanthoma elasticum was made. A skin biopsy was taken from a papular lesion on the neck. Elastic tissue stain (Verhoeff van-Gieson) of the histopathological section showed irregular clumps of elastic fibres in the mid-dermis along with areas of calcification. The features were consistent with pseudoxanthoma elasticum. The patient was sent for thorough cardiovascular evaluation.
Pseudoxanthoma elasticum is a rare inherited disorder of connective tissue affecting principally the dermis of skin, media, and intima of blood vessels and Bruch’s membrane of the eye. The incidence of the disease is about one in 160 000. Two autosomal dominant and three autosomal recessive forms have been described with variable expression of the clinical features. In about 90% of the cases, the inheritance is autosomal recessive. The genetic defect of the disorder is located on chromosome 16p13.1. Histopathologically there is widespread elastorrhexis along with dystrophic calcification of the damaged elastic fibres.
Skin shows characteristic small, yellowish papules, present classically along the sides of neck, giving rise to “Moroccan leather” or “plucked chicken skin” appearance. Other sites of predilection are the axillae, periumbilical area, groin, perineum, and thigh. Similar lesions may occur in soft palate, inner aspect of the lips, and vagina. In older individuals, the involved skin is lax and hangs in large folds. Absence of skin lesions does not exclude pseudoxanthoma elasticum.
The commonest ocular change is the presence of angioid streaks and they are usually asymptomatic and occur in almost all patients with pseudoxanthoma elasticum. Progressive visual dimness, retinal haemorrhage, and occasionally total blindness may occur. Other associated ocular anomalies are drusen, leopard spotting, or a “string of pearls” appearance of the macula. Unaffected family members may have abnormal visibility of the choroidal vessels.
Generalised involvement of all large and medium sized arteries occurs. Manifestations of cardiovascular diseases may start in childhood as decreased peripheral pulses, intermittent claudication, hypertension, angina at younger age, myocardial infarction, and sudden death. Risk of cardiovascular diseases may be correlated with presence of angioid streaks.
Associations with Marfan’s syndrome, scleroderma, and perforating elastosis have been reported. Hypercalcaemia, hyperphosphataemia, and abnormal metabolism of vitamin D are also associated biochemical abnormalities.
Diagnosis depends on clinical and histopathological features. Management is mostly preventive, reducing cardiac risk factors, taking care of ophthalmic and cardiovascular complications, screening of first degree relatives by ophthalmoscopy, and genetic counselling.