Pathology B2 Skin - Disorders of Epidermal Appendages, Panniculitis, and Infection

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Acne Vulgaris

Occur as a result of physiologic, hormonal variations, and alterations in hair follicles
- occur in middle to late teens
- males have it more severe
- induced/exacerbated by drugs, occupational contactants, coal, occulsive conditiosn, cosmetics, tropical climates
Noninflammatory
- open comedones: small follicular papules containing black, central, black keratin plug (color due to oxidation of melanin pigment)
Inflammatory
- closed comedones: follicular papules w/o visible central plug
- since keratin plug blocked..susceptible to rupture and inflammation
- erythematous papules, nodules, pustules

Pathogenesis: Endocrine factors - androgens, bacterial lipases of propionibacterium acnes break down sebaceous oils -> irritate fatty acids --> inflammation
Tx: inhibit lipases..vitamin A derivative (retinoic acid) -> antisebaceous actino

Rosacea

Four stages:
1) flushing episodes
2) persistent erythema and telangiectasia
3) pustules and papules
4) rhinophyma - permanent thickening of nasal skin by conflueny erythematous papules and follicular prominence
- affects females more

Pathogenesis: High cutaneous levels of antimicrobial peptide cathelicidin (mediator of innate immune response)
- inappropriate activation of innate immune response

Pannicultis: Erythema Nodosum and Erythema Induratum

Pannicultis: inflammatory rxn in subcutaneous adipose tissue, can affect CT septa or lobules of fat, involves lower leg usually, has subacute chronic course

Erythema nodusum: most common, occurs generally w/ infections, presents poorly defined, tender, erythematous plaques and nodules, will flatten and become bruiselike, fever malaise

Erythema induratum: uncommon, primary vasculitis affecting deep vessels supplying lobules of subcutis w/ subsequent necrosis and inflamm. w/in fat. Occurs usually W/O underlying disease

Verrucae (Warts)

Caused by human papillomaviruses, self-limiting, and common in children and adolescents
Veruca vulgaris: most common
- papules occur on hands
Verruca plantaris/palmaris: on soles and palms
Condyloma acuminatum (veneral wart) - perianal areas and rectum
- soft, tan, cauliflower-like masses

Pathogenesis: Variants assoc. w/ HPV subtypes (HPV 16- dysplasia; HPV 6,11 - warts; HPV 5,8 - squamous cell carcinoma)

Molluscum Contagiosum

Viral disease of skin caused by poxvirus
-brick-shaped, dumbbell-shaped DNA core
- spread by direct contact in children and young adults usually
- lesions on skin and mucous membranes, trunk, anogenital areas
- curd-like material can be expressed from central umbilication

Impetigo

Superficial bacterial infection of skin, highly contagious, seen in children or adults of poor health
- affects face and hands
- erythematous macule, small pustules, when erode they form honey-colored crust -> if not removed can form bullous and epidermal damage
Impetigo contagiosa and impetigo bullosa
- both caused by staph aureus
- contagiosa caused by beta-hemolytic streptococci

Pathogenesis: Innate immune response cause formation of scale crust (scab). Bacteria produce TOXIN that cleaves desmoglein 1 (responisble for cell-cell adhesion)
NOTE: Pemphigus foliaceus caused by AB..NOT toxin!

Superficial Fungal Infections

Confined to the stratum corneum and caused primarily by dermatophytes (organisms that grow in soil, animals)

Tinea capitis - occurs in children, dermatophytosis of scalp, hairless patches of skin
Tinea barbae - uncommon, dermatophyte infection of beard area
Tinea corporis - common, due to excessive heat and humidity, exposure to infected animals, chronic dermatophytosis of feets or nails
Tinea cruris - inguinal areas of obese men during warm weather
Tinea pedis/ATHLETE'S FOOT - erythema and scaling due to bacterial superinfection, not directly related to primary dermatophytosis
-> spread to nails onchomycosis (discoloration, thickening, deformity of nail plate)
Tinea versicolor - upper turnk, caused by Malassezia furfur (yeast, not dermatophyte), lesions ligher or darker than surrounding skin

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