Porth's Essentials of Pathophysiology, 4e

1155

Disorders of Skin Integrity and Function

C h a p t e r 4 6

a mildly scaling lesion to a painful, exudative, erosive, inflamed lesion with fissuring. Lesions often are accom- panied by pruritus, pain, and foul odor. Mild forms are more common during dry environmental conditions. Exacerbations occur as a result of hot weather, sweat- ing, and exercise or when the feet are exposed to mois- ture, occlusive shoes, and communal swimming. Tinea of the hand ( Tinea manus ) is usually a second- ary infection with tinea pedis as the primary infection. In contrast to other skin disorders, it usually occurs only on one hand. The characteristic lesion is a blister on the palm or finger surrounded by erythema. Chronic lesions are scaly and dry. Cracking and fissuring may occur. The lesions may spread to the plantar surfaces of the hand. If chronic, tinea manus may lead to tinea of the fingernails. Simple forms of tinea pedis and tineamanus are treated with topical applications of antifungals. Complex cases are treated with oral antifungals. Other treatment and preventive measures include careful cleaning and drying of affected areas. Tinea of the Nails. Tinea unguium is a dermatophyte infection of the nails. It is a subset of a condition called onychomycosis, which includes dermatophyte, nonder- matophyte, and candidal infections of the nails. The infection often begins at the tip of the nail, where the fungus digests the nail keratin (Fig. 46-4). In some cases, it may be caused by a crushing injury to a toenail or the spread of tinea pedis. Initially, the nail appears opaque, white, or silver. The nail then turns yellow or brown. The condition often remains unchanged for years. During this time it may involve only one or two nails and may produce little or no discomfort. As the infection spreads, the nail thickens and cracks and the nail plate separates from the nail bed. The standard for the diagnosis of fungal nail dis- ease is a positive result on microscopic examination and culture of nail clippings with subungual debris. Persons with minimal toenail involvement and no associated symptoms may not require treatment.

of a pustular, scaly, round patch with broken hairs. A secondary bacterial infection is common and may lead to a painful, circumscribed, boggy, and indurated lesion called a kerion . The highest incidence is among children and farmers who work with infected animals. Both the noninflammatory and inflammatory forms of tinea capitis are treated with oral griseofulvin or syn- thetic antifungal agents that penetrate the hair shafts. 5–7 Topical ointments or shampoos are sometimes indicated in addition to oral medications, both to decrease the spore population and to protect household members. Because of the lower fatty acid content in the sebum of young children, several of the topical antifungal agents are prepared with fatty acid bases. Wet packs, medicated shampoos, steroids, and antibiotics may be prescribed for secondary infections that occur. Tinea of the Foot and Hand. Tinea pedis (athlete’s foot) is the most common fungal dermatosis, primar- ily affecting the spaces between the toes, the soles, or the sides of the feet (Fig. 46-3). The lesions vary from FIGURE 46-2. Ringworm or tinea of the scalp (tinea capitis) caused by the Microsporum species. (From the Centers for Disease Control and Prevention Public Health Image Library. No. 2940. Courtesy of Dr. Lucille K. Georg.)

FIGURE 46-4. Onychomycosis due to Trichophyton rubrum, right and left great toes. (From the Centers for Disease Control and Prevention Public Health Image Library. No. 579. Courtesy of Edwin P. Ewing, Jr.)

FIGURE 46-3. Chronic tinea of the sole caused by Trichophyton rubrum. (From the Centers for Disease Control and Prevention Public Health Image Library. No. 15441.)