Diseases of collagen and elastic tissue

The skin contains collagen types I, III and V within the dermis, type IV in the basement membrane, type VII in the anchoring fibrils and type VIII in the endothelium . Abnormalities of these can give rise to various
skin disorders. Ehlers-Danlos syndrome This is a heterogeneous group of diseases in which at least nine different varieties have been described. Hyperextensibiliry, fragility and bruising of the skin occur to a varying degree with each of the diseases and it is accompanied by the hypermobility of joints. Fragility of blood vessels occurs, and rarely aortic rupture.
The patterns of inheritance are varied and can be utosomal recessive, autosomal dominant or X-linked recessive.
The skin is velvety to the touch an hyperextensible but recoils normally on stretching. Trauma or laceration of the skin can lead to tissue-paper scars and poor wound healing. Pseudotumours may occur over the elbows and knees; they consist principally of fat, but may show signs of calcification.

Solar elastosis

Degradation of elastric fibrils in the skin normally occurs with ageing. This usually begins in early adult life but changes are more noticeable in the sixties and seventies. The clinical features are characterized by yellowish papules or plaques and wrinkling and are usually associated with pigmentation and keratoses on exposed skin. Cutis laxa (generalized elastolysis) This is a rare disease in which there are a number of variants. These are inherited as autosomal recessive, Xlinked recessive or dominant traits. A defect in the crosslinking of elastin is suggested, but other abnormalities, including copper deficiency, have been reported. The subsequent changes in the skin, sometimes gross, may be evident at birth or arise at the time of puberty. The disfiguring changes may be severe with extreme laxity of the facial skin and massive folds over the trunk that have no recoil on stretching. Joint hypermobility is not a common feature.

Pseudoxanthoma elasticum

This is a generalized disorder of elastic tissue. The pathogenesis is unknown, and both autosomal dominant and recessive modes of transmission are seen. The skin, eyes and vascular structures are involved. Cutaneous features are seen in childhood and are most evident over flexural surfaces and at the sides of the neck. Initially there is an accentuation of skin lines or folds and this is followed by thickening around yellowish diamondshaped papules, producing a peau d’orange or pluckedchicken appearance. The skin may be lax and hang in folds. The skin demonstrates very little elastic recoil on stretching. The mucous membranes may also be affected. Long-term and high-dose treatment with D-penicillamine produces similar cutaneous features.Widespread vascular changes are associated with  fibrous proliferation and the deposition of calcium in the media of the arteries. Intermittent claudication and angina pectoris occur at an early age as a result. Gastrointestinal bleeding may be a troublesome feature. Splits in Bruch’s membrane, which contains both elastin and collagen and separates the choroid from the retina, are demonstrated as angioid streaks on ophthalmoscopy.

Marfan’s syndrome

A biochemical defect for this disease has not been identified, and some features of the condition may be seen in association with the Ehlers-Danlos syndrome or with homocystinuria. Inheritance is usually in an autosomal dominant manner. Striae distensae are the only common dermatological sign, and the most impressive changes affect the skeleton. The facial appearance of affected patients may be distinctive, with elongation and asymmetry. A high-arched palate, although frequently described, is not a common feature. A tall stature, long thin digits and alteration in the body proportions are seen; the distance from the soles to the pubis (lower segment) is greater than the distance from the pubis to the vertex (upper segment). The arm span, measured from the extended fingers, often exceeds the height of the patient.

J0 INTs. A laxity ofligaments may give rise to dislocation of joints such as the jaw or patellae. Steinberg’s sign occurs when the thumbs are adducted over the palm and their tips are seen to cross the ulnar border of the hand. Inguinal or femoral hernias are often seen. RESPIRATORY SYSTEM. Pulmonary changes include hernia of the diaphragm, emphysema and spontaneous pneumothorax.
CARDIOVASCULAR SYSTEM. Cardiovascular symptoms follow the degeneration in the media of vessel walls. The aortic valve ring may dilate and produce an incompetent valve, with the mitral valve frequently involved, producing the billowy or prolapsed valve syndrome (see p. 597). Aneurysm formation may occur, usually in the ascending aorta, and may be followed by dissection and/or rupture.

EYES. Weakness of the suspensory ligament of the lens may cause dislocation; this is a common clinical feature of the disease.

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