Epidemiology The World Health Organization (WHO) has committed itself to eliminating Hansen disease as a public health problem, but the disease remains endemic in certain regions, with 95% of cases reported from 16 countries. Brazil, India, and Indonesia account for 80% of all cases worldwide. Although 90% of diagnosed U.S. cases are imported, Hansen disease is endemic in the coastal southeastern United States and in Hawaii.…

Tuberculosis No ideal classification scheme exists for cutaneous tuberculosis (TB), but the system listed here is logical and takes into account the mechanism of disease acquisition. Unfortunately, unlike in Hansen disease, these categories do not correlate perfectly to host immunity. The four major categories of cutaneous TB are as follows: 1 Inoculation from an exogenous source (primary inoculation TB, TB verrucosa cutis) 2 Endogenous cutaneous spread…

Superficial and Deep Mycoses Fungal infections, including dermatophytes and candida, are the most common type of infection worldwide. Cutaneous infections are divided into superficial (those that affect mostly the skin) and deep (those that are typically more invasive) mycoses. In addition immunosuppressed patients are at high risk for opportunistic fungal infections, including from molds and other saprophytic fungi that are not typically pathogens in normal hosts.…

Bacterial infections in the skin often have distinct morphologic characteristics that should alert the clinician that a potentially treatable and reversible condition exists. These cutaneous signs may be an indication of a generalized systemic process or simply an isolated superficial infection. Patients who have immunodeficiencies or are immunosuppressed may acquire severe or refractory pyogenic infections. Patients with atopic dermatitis are also predisposed to bacterial infections due…

Acne Vulgaris Clinical Features Acne vulgaris is a chronic inflammatory disease of the pilosebaceous follicles, characterized by comedones, papules, pustules, nodules, and often scars. The comedo is the primary lesion of acne. It may be seen as a flat or slightly elevated papule with a dilated central opening filled with blackened keratin (open comedo or blackhead) ( Fig. 13.1 ). Closed comedones (whiteheads) are usually 1-mm…

Lichen Planus Lichen planus (LP) is a common, pruritic, inflammatory disease of the skin, mucous membranes, and hair follicles. It occurs throughout the world, in all races. Cutaneous LP affects 0.3% of men and 0.1% of women. Oral LP affects 1.5% of men and 2.3% of women. It may be familial in rare cases. The pattern of LP detected and the age distribution vary among various…

Pityriasis Rosea Clinical Features Pityriasis rosea is a mild inflammatory exanthem characterized by salmon-colored thin papules and plaques that are at first discrete but may become confluent ( Fig. 11.1 ). The individual patches are oval or circinate and covered with finely crinkled, dry epidermis, which often desquamates, leaving a collarette of scaling in the center. When stretched across the long axis, the scales tend to…

Seborrheic Dermatitis Clinical Features Seborrheic dermatitis is common, occurring in 2%–5% of the population. It is a chronic, superficial, inflammatory disease with a predilection for the scalp, eyebrows, eyelids, nasolabial creases, lips, ears ( Fig. 10.1 ), sternal area, axillae, submammary folds, umbilicus, groins, and gluteal crease. The disease is characterized by scaling on an erythematous base. The scale often has a yellow, greasy appearance. Itching…

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 the dermis and are responsible for dermal volume and texture. Normally, the sulfated acid mucopolysaccharide chondroitin sulfate and heparin are the primary dermal mucins. In certain…

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 ground substance. Lupus Erythematosus Lupus may manifest as a systemic disease or in purely cutaneous forms. Cutaneous manifestations of LE are classified as in Box 8.1…

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 flushing may be associated with perspiration, as is flushing induced by high ambient temperature, fever, or consumption of alcohol or hot or spicy foods and beverages.…

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 an eruption in most people who come in contact with it. Allergic contact dermatitis is an acquired sensitivity to various substances that produce inflammatory reactions only…

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 at times is used synonymously for atopic dermatitis (atopic eczema). The acute stage generally presents as a red edematous plaque that may have grossly visible, small,…

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, and fine intraepidermal C-neuron filaments. Approximately 5% of the afferent unmyelinated C neurons respond to pruritogenic stimuli. Itch sensations in these nerve fibers are transmitted via…

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 all body structures sensitive to electromagnetic wave radiation of varying frequencies, such as x-rays and ultraviolet (UV) rays. The skin, which is exposed to so many…

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, are essential to arrive at a diagnosis. The same disease may show variations under different conditions and in different individuals. The appearance of the lesions may…

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 the dermis is the fibrillar structural protein collagen. The dermis lies on the panniculus, which is composed of lobules of lipocytes separated by collagenous septa that…