inflammatory_skin_diseases-94-109.pdf

Acne Vulgaris • Virtually universal in the middle to late teenage years, • Affects both males and females, although males tend to have more severe disease. • is seen in all races but is usually milder in people of Asian descent. • may be induced or exacerbated by drugs (corticosteroids, adrenocortic...

Acne Vulgaris • Virtually universal in the middle to late teenage years, • Affects both males and females, although males tend to have more severe disease. • is seen in all races but is usually milder in people of Asian descent. • may be induced or exacerbated by drugs (corticosteroids, adrenocorticotropic hormone, testosterone, gonadotropins, contraceptives, trimethadione, iodides, and bromides), occupational exposures (cutting oils, chlorinated hydrocarbons, and coal tars), and conditions that favor occlusion of sebaceous glands, such as heavy clothing, cosmetics, and tropical climates. • Some families seem to be particularly prone to acne, suggesting a hereditary component. Acne Vulgaris • Acne is divided into noninflammatory and inflammatory types, although both types may coexist. Noninflammatory acne may take the form of open and closed comedones. • Open comedones are small follicular papules containing a central black keratin plug. This color is the result of oxidation of melanin pigment (not dirt). • Closed comedones are follicular papules without a visible central plug. Because the keratin plug is trapped beneath the epidermal surface, these lesions are potential sources of follicular rupture and inflammation. Acne Vulgaris • The pathogenesis of acne is incompletely understood and is likely multifactorial. • At least four factors contribute to its development: (1) keratinization of the lower portion of the follicular infundibulum and development of a keratin plug that blocks outflow of sebum to the skin surface, (2) hypertrophy of sebaceous glands during puberty under the influence of androgens, (3) lipase-synthesizing bacteria (Propionibacterium acnes) colonizing the upper and midportion of the hair follicle, converting lipids within sebum to proinflammatory fatty acids, and (4) secondary inflammation of the involved follicle Acne Vulgaris • Inflammatory acne is marked by erythematous papules, nodules, and pustules . • Severe variants (e.g., acne conglobata) result in sinus tract formation and dermal scarring. • Depending on the stage of the disease, open or closed comedones, papules, pustules, or deep inflammatory nodules may develop. • Open comedones have large, patulous orifices, whereas those of closed comedones are identifiable only microscopically . • Variable infiltrates of lymphocytes and macrophages are present in and around affected follicles, and extensive acute inflammation accompanies follicular rupture. • Dermal abscesses may form in association with rupture and lead to scarring. Acne Vulgaris Rosacea • Rosacea is a common disease of middle age and beyond, affecting up to 3% of the US population, with a predilection for females. • Four stages are recognized: • • • • (1) flushing episodes (pre-rosacea), (2) persistent erythema and telangiectasia, (3) pustules and papules, and (4) rhinophyma—permanent thickening of the nasal skin by confluent erythematous papules and prominent follicles. Rosacea • Pathogenesis. • Individuals with rosacea have high cutaneous levels of the antimicrobial peptide cathelicidin, an important mediator of the cutaneous innate immune response. Panniculitis • Erythema Nodosum and Erythema Induratum Panniculitis • Panniculitis is an inflammatory reaction in the subcutaneous adipose tissue that may preferentially affect (1) the lobules of fat, or (2) (2) the connective tissue that separates fat into lobules. Panniculitis often involves the lower legs. Erythema nodosum is the most common form Erythema nodosum • poorly defined, tender, erythematous plaques and nodules that may be more readily palpated than seen. • often associated with infections, drug administration, sarcoidosis, inflammatory bowel disease, and certain malignant neoplasms, but many times a cause cannot be identified. • Fever and malaise may accompany the cutaneous signs. • considered to be caused by a delayed hypersensitivity reaction to microbial or drug related antigens. In some cases immune complexes have been implicated but in many cases the pathogenesis remains mysterious. • Over the course of weeks, lesions usually flatten and become bruiselike, leaving no residual clinical scars, while new lesions develop. • Biopsy of a deep wedge of tissue to generously sample the subcutis is usually required for histologic diagnosis. Erythema induratum • Erythema induratum is an uncommon type of panniculitis that affects primarily adolescents and menopausal women. • Although the cause is not known, most observers regard this as a primary vasculitis of deep vessels supplying the fat lobules of the subcutis; the associated vascular compromise leads to fat necrosis and inflammation. • Erythema induratum presents as an erythematous, slightly tender nodule that usually goes on to ulcerate. • Originally considered a hypersensitivity response to tuberculosis, erythema induratum today most commonly occurs without an associated underlying disease. Panniculitis • Many other types of panniculitis have also been described: • Weber-Christian disease (relapsing febrile nodular panniculitis) is a rare form of lobular, nonvasculitic panniculitis seen in children and adults. It is marked by crops of erythematous plaques or nodules, predominantly on the lower extremities, created by deep-seated foci of inflammation containing aggregates of foamy macrophages admixed with lymphocytes, neutrophils, and giant cells. • Factitial panniculitis is a form of secondary panniculitis caused by self-inflicted trauma or injection of foreign or toxic substances. • Rare types of T-cell lymphoma home to fat lobules, producing fat necrosis and superimposed inflammation that mimics panniculitis. • Lupus erythematosus may occasionally cause inflammation of the subcutis and an associated panniculitis MOLLUSCUM CONTAGIOSUM • Molluscum contagiosum is a common, self-limited viral disease of the skin caused by a poxvirus. • The virus is the largest pathogenic poxvirus in humans and one of the largest viruses in nature. • Infection is usually spread by direct contact, particularly among children and young adults. MOLLUSCUM CONTAGIOSUM • Multiple lesions may occur on the skin and mucous membranes, with a predilection for the trunk and anogenital areas. • Individual lesions are firm, often pruritic, pink to skin-colored umbilicated papules, generally ranging in diameter from 0.2 cm to 0.4 cm. • Rarely, “giant” forms occur measuring up to 2 cm in diameter. • A curd-like material can be expressed from the central umbilication. Smearing this material onto a glass slide and staining with Giemsa often shows diagnostic molluscum bodies. • On microscopic examination, lesions show cuplike verrucous epidermal hyperplasia. The diagnostically specific structure is the molluscum body, which occurs as a large (up to 35 µm), ellipsoid, homogeneous, cytoplasmic inclusion in cells of the stratum granulosum and the stratum corneum. • In the hematoxylin and eosin stain, these inclusions are eosinophilic in the blue-purple stratum granulosum and acquire a pale blue hue in the red stratum corneum. Numerous virions are present within molluscum bodies. MOLLUSCUM CONTAGIOSUM MOLLUSCUM CONTAGIOSUM