Porth's Essentials of Pathophysiology, 4e

he skin serves as the interface between the body’s internal organs and the external environment. Therefore, skin disorders reflect a combination of envi- ronmental and internal factors. Sunlight, infectious organisms, chemicals, and physical agents all play a role in the pathogenesis of skin diseases. Although most of the disorders in this chapter are intrinsic to the skin and its integuments, the hair and nails, these structures also provide observable signs of many systemic disorders. Primary Disorders of the Skin A dermatosis is any skin condition involving acute or chronic lesions or eruptions. Primary dermatoses are those originating in the skin. They include infectious processes, acne, rosacea, papulosquamous dermatoses, allergic disorders, and drug reactions. Although most of these disorders are not life-threatening, they can affect the quality of life. Infectious Processes Normally, the skin flora, sebum, immune responses, and other protective mechanisms defend against serious sys- temic infections. However, the skin frequently succumbs to attack by microorganisms, including fungi, bacteria, and viruses. Superficial Fungal Infections Fungi are free-living, saprophytic, plantlike organisms, certain strains of which are considered part of the nor- mal skin flora (see Chapter 14). There are two types of fungi: yeasts and molds. Yeasts, such as Candida albicans , grow as single cells and reproduce asexually. Molds grow in long filaments called hyphae. Fungal infections of the skin or mycoses are commonly classi- fied as deep or superficial. 1–3 Deep fungal infections of the skin primarily involve the dermis and subcutaneous tissue, and may extend into deeper tissues. In contrast, superficial fungal infections, commonly known as tinea Disorders of Skin Integrity and Function 46 C h a p t e r T

Primary Disorders of the Skin Infectious Processes

Superficial Fungal Infections Bacterial Infections Viral Infections

Pustular Disorders Acne Vulgaris

Acne Conglobata Rosacea Allergic and Hypersensitivity Dermatoses Atopic Dermatitis Urticaria Drug-Induced Skin Eruptions Papulosquamous Dermatoses Psoriasis Pityriasis Rosea Lichen Planus Lichen Simplex Skin Disorders due to Ultraviolet Radiation, Heat, and Pressure Injury Ultraviolet Radiation Ultraviolet Radiation Skin Damage Drug-induced Photosensitivity Thermal Injury Classification of Burns Systemic Complications Emergency and Long-Term Treatment Pressure Ulcers Mechanisms of Development Prevention and Treatment Nevi and Skin Cancers Nevi Skin Cancer Age-Related Skin Conditions Skin Manifestations of Infancy and Childhood Skin Disorders of Infancy Pigmented and Vascular Birthmarks Skin Manifestations of Common Infectious Diseases Skin Manifestations and Disorders in the Elderly Normal Age-Related Changes Skin Lesions Common Among the Elderly Malignant Melanoma Basal Cell Carcinoma Squamous Cell Carcinoma

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