Section 14: Genodermatoses

Pseudoxanthoma elasticum This is a generalized condition in which elastic fibers are degenerative. Clinical signs of the phenomenon can be recognized in the skin and eyes. In the skin, patches of yellowish discoloration and general laxness or redundancy develop on the neck (“chicken skin”), in the axillae, and in other places, such as the fossae of limbs and the inguinal folds, where considerable movement of skin is normal. In the eye, angioid streaks can be seen. They represent the result of faulty elastic fibers in Bruch membrane and generally precede the cutaneous changes. These eye changes frequently result in the loss of central vision and sometimes result in almost complete blindness. Peripheral vision is maintained.

Pseudoxanthoma elasticum Gastrointestinal hemorrhage is the most serious acute consequence, but slower structural damage in various organs may result in hypertension, coronary artery occlusion, diabetes mellitus, thyroid dyscrasia, or ectopic calcinosis. The disease may be inherited in autosomal recessive or autosomal dominant fashion. This entity is caused by mutations in the ABCC6 gene mapped to chromosome 16p13.1.

Cutis laxa This disorder may be caused by mutations in genes that are responsible for the formation, assembly, or function of elastic fibers, or may be later in life and related to the destruction of elastic fibers. As seen in this patient, the skin hangs in folds and produces an appearance of premature aging. Because elastic fibers are affected in all organ systems, intestinal and urinary bladder diverticula, rectal prolapse, inguinal hernias, and pulmonary emphysema occur frequently. The last of these is associated with significant mortality.

Ehlers-Danlos syndrome This syndrome is actually a collection of six major genetic types with the common features of hyperextensible skin and joints, easy bruising, defective wound healing, and blood vessel fragility. Distinct abnormalities in collagen synthesis have been identified in some of the varieties of Ehlers-Danlos syndrome. The result of the anomaly is extreme stretchability but unimpaired elasticity (ie, the ability to return to normal after stretching). The figures illustrate the phenomenon; Fig. 14-5 shows skin of the neck and Fig. 14-6 shows skin of the elbow extended several times more than normal skin can be pulled out.

Ehlers-Danlos syndrome In these illustrations, more of the hyperextensible phenomena and the consequences of functional abnormality of elastic fibers and collagen are shown. Figure 14-7 shows hyperextensibility of joints, ...