Within the dermis is a fibrillar matrix, termed ground substance, composed of proteoglycans and glycosaminoglycans. These acid mucopolysaccharides, produced by fibroblasts, are highly hygroscopic, binding about 1000 times their own volume in water. They are critical in holding water in…
Lupus erythematosus (LE), dermatomyositis (DM), scleroderma, rheumatoid arthritis, Sjögren syndrome, eosinophilic fasciitis, relapsing polychondritis, and related disorders are classified as connective tissue diseases. Basic to all these is a complex array of autoimmune responses that target or affect collagen or…
Flushing Flushing presents with transient erythema, usually localized to the face, neck, and upper trunk, and a sensation of warmth. Flushing may be physiologic or pathologic; though normally benign, causes range from emotions to hormones to medications and malignancy. Menopausal…
Contact Dermatitis There are two types of dermatitis caused by substances coming in contact with the skin: irritant dermatitis and allergic contact dermatitis. Irritant dermatitis is an inflammatory reaction in the skin resulting from exposure to a substance that causes…
Eczema The word eczema seems to have originated in 543 ad and is derived from the Greek word ekzein, meaning to “to boil forth” or “to effervesce.” The term encompasses such disorders as dyshidrotic eczema and nummular eczema (NE), but…
Pruritus Pruritus, commonly known as itching, is a sensation exclusive to the skin. It may be defined as the sensation that produces the desire to scratch. Pruritogenic stimuli are first responded to by keratinocytes, which release a variety of mediators,…
The body requires a certain amount of heat, but beyond definite limits, insufficient or excessive amounts are injurious. The local action of excessive heat causes burns or scalds; undue cold causes chilblains, frostbite, and congelation. Thresholds of tolerance exist in…
In some patients, the appearance of skin lesions may be so distinctive that the diagnosis is clear at a glance. In others, subjective symptoms and clinical signs alone are inadequate, and a complete history and laboratory examination, including a biopsy,…
Skin is composed of three layers: the epidermis, dermis, and subcutaneous fat (panniculus) ( Fig. 1.1 ). The outermost layer, the epidermis, is composed of viable keratinocytes covered by a layer of keratin, the stratum corneum. The principal component of…