• verruca vulgaris
• molluscum contagiosum
• herpes virus simplex

• usually seen in children and adolescents, although may be encountered at any age
• transmission
  • direct contact between individuals
  • autoinoculation
• causative agent- HPV

• gross appearance
  • circumscribed, verrucous
  • hyperkeratotic
  • papules
  • single OR in groups
• common locations (can be anywhere on skin)
  • dorsum of the hands and fingers
  • feet and toes
• prognosis- generally self limited, regress spontaneously 6 mnths-2 yrs

• weight bearing areas of the soles and on the palms

• penis
• female genitalia
• urethra
• perianal areas
• rectum

Cauliflower like mass

• epidermal papillomatous proliferation
• hyperkeratosis
• viral induced vacuolization of keratinocytes
• clear vacuolization of superfical layers of epithelial cells (koloiocytosis)- characteristic of HPV

• confined to stratum corneum
• causative agents- dermatophytes

• tinea capitis
• tinea barbae
• tinea corporis
• tinea cruris
• tina pedis
• onychomycosis
• tinea vesicolor

• usually in children (RARE in infants, adults)
• location- scalp dermatophytosis
• gross appearance
  • asymptomatic, hairless patch of skin
  • associated with:
    • mild erythema
    • crust formation
    • scaling

• location- superficial fungal infection of body surface
• affects all ages, but especially children
• gross appearance
  • expanding, round, slightly erythematous plaque
  • elevated scaling border

• common location- inguinal areas
• common group- obese men during warm weather
• predisposing factors
  • heat
  • friction
  • maceration
• gross appearance
  • usually starts on upper inner thighs and gradually extends
  • moist, red patches
  • raised, scaling borders

• gross appearance- diffuse erythema and scaling
• location- often initially localized to web spaces

• causative agent- Malassezi furfur (this is a yeast, NOT dermatophyte)
• common location- upper trunk
• gross appearance
  • groups of macules of all sizes
  • lighter or darker than surrounding skin
  • with fine peripheral scale

• focal perakeratosis
• mild superficial inflammation

• impetigo
• acne vulgaris

• commonly in pre school aged children, esp. in warm, humid climates
• predisposing factors (any minor trauma)
  • chicken pox
  • arthopod bite
  • abrasion
  • laceration
  • burns
• is a complication of:
  • AIDS
  • DM
  • other skin diseases that cause a break in the skin barrier
    • scabies
    • atopic dermatitis
    • Darier's disease

• gross appearance
  • begin as small vesicles or pustles
  • may progress into honey colored crusted plaques
• causative agents
  • group A strep (beta hemolytic)
  • S. aureus
  • if newborn: group B strep

• streptococcal infection
• subcorneal (stratum corneum) accumulation of neutrophils

1. block in sebum filled hair follicle (folliculitis)
2. promotes overgrowth of bacteria Propionibacterium acnes (normally present in hair follicle)
3. activity of Propionbacterium acnes within the comedone (abnormal follicular keratinization) promotes release of free FA's from sebum
4. this cause inflammation within the cyst
5. results in rupture of cyst (follicular rupture)
6. inflammatory foreign body reaction develops as a result of extrusion of oily and keratinous debris from cyst

• androgen induced sebum production that leads to propionibacterium acnes proliferation
• faulty desquamation of follicular wall that produces a keratin plug in the follicle
• probable immunologic HS to P. acnes that produces lesional inflammation

• due to combo of autoimmune, genetic, environmental factors
• loss of basilar melanocytes and melanin resulting in depigmentation

• cause- increase in amount of melanin in the basal layer of epidermis (NO increase in number of melanocytes)
• appear in first 3-5 yrs of life
• increase in number, size, depth of pigmentation following continued sun exposure

• increased amount of melanin in melanocytes and basal keratinocytes
• can have normal or increased numbers of melanocytes in basal layer

• proliferation of benign, generally cuboidal melanocytes in nests
• location- could be at:
  • epidermis (junctional nevus)
  • dermis (dermal nevus)
  • both dermis and epidermis (compound nevus)
• microscopic features
  • symmetric lesion
  • maturation with increasing depth of dermis

• at least 5 mm diameter
• must have one or more of unusual features (some of features of melanoma, but relatively subtle compared to melanoma):
  • asymmetry
  • variegation of pigmentation
  • irregular border
  • surrounding pigmented rim or "flare" around the central elevated portion

• cytologic atypia
  • irregularly shaped, dark staining nuclei
• dermis underlying atypical cells shows linear/lamellar fibrosis

• asymmetry
• border irregularity
• color
• diameter greater than 6 mm

• genetics
  • mutation to diminish activity of tumor suppressing RB gene in familial and sporadic melanomas
  • CDKN3A mutation (codes for three different tumor suppressors) in autosomal dominant melanomas
    • p16/INK4a clearly implicated in human melanomas
• sun exposure

• atypical melanocytes proliferation with pagetoid spread
• irregular nesting
• confluence of nests assymetry and broad growth
• lost of normal nevus

• greatly increased risk
• patients whose family members have atypical nevi and familial malignant melanoma have 100x greater risk of devloping malignant melanoma over their lifetimes

• tumor depth (Breslow method)
  • measure from granular layer of epidermis to deepest part of tumor
• number of mitoses
• evidence of tumor regression (presumed to be due to host immune response)
• presence and number of tumor infiltrating lymphocytes
• gender
• location (central body or extremity)