| Disease | Epidemiology | Path | diagnsosis | Histo | Gross | Tx | |
| Vocabulary | Hyperkeratosis (hyperplasia of stratum corneum) | Parakeratosis (retention of nuclei in stratum corneum) | Hypergranulosis (hyperplasia of stratum granulosum) | Acanthosis (epidermal hyperplasia)[1] | Papillomatosis (surface undulations due to hyperplasia of papillary dermis) | Dyskeratosis (abnormal keratinization) | Acantholysis (loss of intercellular connections) |
| Spongiosis (increased intercellular edema in epi) | Exocytosis (Inflammatory cell epidermal infiltration) | Erosion (incompete epidermal loss) | ulceration (complete epidermal loss) | Lentiginous (basal layer linear melanocyte proliferation) | vacuolization (vacuoles b/w cells) | ||
| Melanocytic disease | |||||||
| Melanocytes | Originate in neural crest and migrate to basal layer of epidermis (8wk), hair matrix, inner ear, uveal tract, and leptomeninges | Converts tyrosine to melanin and transfers to keratinocyte via dendritis process. | Dendritic cells dispersed along basal layer (1 for ervery 10 keratinocyts) | ||||
| Vitiligo | 1) All ages and races, 2) 50% occur before 20yo, 3) Assd w/ autoimmune disorders (Addison, perncious anemia, autoimmune thyroiditis[2] | 1) DEF: Partial or complete loss of melanocytes in epidermis., 2) MECH: Ab vs. melanocytes, 3) Repigmentation through melanocyte precursor in hair follicle ostia | Flat, well-demarcated | loss of melanocytes | loss of pigment | ||
| Ephilis (freckle) | 1) most common pigmented lesion of childhood | 1) Appear in childhood after sun exposure, 2) fade and reappear with exposure | increased melanin within basal keratinocytes (normal number of melanocytes) | 1) 1-10mm diameter, 2) tan-red or light brown macule | |||
| Lentigo | 1) All ages, 2) Kids = lentigo simplex; adults = solar lentigo (sun damage) | Local hyperplasia of malanocytes which do not darken when exposed to sun | 1) increased melanocytes along the basal layer, 2) elongation and rete thinning | ||||
| Junctional Nevus | 1) Melanocytes that have lost their dendritic processes, 2) Mole | junctional proliferation --> | Proliferation of nevus cells are tips of rete ridges | Macular, evenly diffiuse color | |||
| Compound Nevus | junctional and dermal proliferation --> | nevus cells invade dermis and raise skin | Nodule (slightly elevated) | ||||
| Intradermal Nevus | Dermal proliferation --> | Dermal nevus proliferation | Nodule (elevated mole) | ||||
| Spitz Nevus | 1) Most common in children | L) Junctional nests with dermal maturation, R) large spindle and epitheliod cells | |||||
| Blue Nevus | 1) maybe confused w/ melanoma | 1) non-nested, dendritis, heavily pigmented | black/blue nodule | ||||
| Congenital Nevus | 1) Present at birth, 2) large (giant) variant melanoma risk increase, 3) may have hair | 1) look like conventional nevi w/ growth around adnexa and neovascular bundle | |||||
| Halo Nevus | Host immune response to nevus cells and adjacent melanocytes | lymphocytic infiltrate | halo around nevus | ||||
| Dysplastic Nevus | 1) dyplastic nevi + melanoma FH = 100% melanoma risk, 2) DN + (-)FH = sligh risk increase, 3) AD, | histo | 1) sun and non-sun exposed areas, 2) large, variable pigmentation, irregular borders | ||||
| Melanoma | 1) 8th most common malignancy in US, 2) white, 3)RF: dyplastic & cong. Nevi, past history (900X), FH (8X), XP (1000X), brite/intense/intermitent UV, 4) 4mm = 10yr @ 0%, 5) Sites: skin, oral & anogenital mucosa, esophagus, meninges, eye | 1) GENETICS: Sporadic (PTEN mutation), Familial (meth of CDKN2A; 50% of fam melanoma), 2) Radial (horizontal spread w/ no mets or angiogenesis) & Vertical (nodular lesion with downward growth and angiogenic metastatic potential related to depth) | A (assymetry), B (border irregularity), C (color change), D (diameter >6mm), E (elevation) | Melanoma in situ: Melanocytes have clearing around nucleus. Pagetoid is spread into epidermal layer. Dermal inflammation but no melanocytes | pic | Melanoma | |
| Non-melanotic skin lesion | |||||||
| Seborheic keratosis | 1) middle aged and elderly, 2) spontaneous | 1) may become irritated, but benign and no Tx necessary, 2) Leser-Trelat (paraneoplastic syndrome with explosive onset due most commonly to TGF-a from gastric adenocarcinoma, lymphoma, brca, SCC of lung) | 1) well demarcated w/ uniform benign basaloid proliferation, 2) hyperkeratosis, 3) epi horn cysts | Round, flat velvety plaques appear "stuck on" | |||
| Keratoacanthoma | 1) >50yo M, 2) sun exposed skin: ears, nose, cheek, and dorsum of hand | 1) rapidly developing neoplasm which mimics SCC but may have spontaneous resolution w/o tx, 2) cytologic atypic and mitosis (controversial) | Histo: Keratin filled crater. Well circumscribed cup shape w/ dark blue basal layer. | Histo HP: Enlarged cells with a glassy eosinophilic cytoplasm and abrupt keratinization | Well circumscribed ulcerated tumor with central keratinization | ||
| Actinic Keratosis | 1) Pre-cancerous, 2) Sun-exposed | Series of dysplastic changes related to cumulative sun exposure with elastic degeneration (solar elastosis) due to UV damage. | Gross: plaques | Gross: horns | histo: parakeratosis, atrophy, basal atypica, solar elastosis | ||
| Squamous Cell Carcinoma | 1) 2nd most common skin tumor, 2) RF (indust carcinogens, chronic ulcers, burn scars, arsenic, radiation, chewing tobacco, Betel nut) | 1) UV (inhibits Langerhans cell presentation = defective immunosurveillance), 2) Immunosuppressed (chemo, transplant), 3) Xeroderma pigmentosa (DNA repair defect) | SCC in situ: Atypical keratinocytes through entire epidermis[3] | Invasive: Squamous eddies "pearls" and with nesting | 1) In situ: sharply defined, red, scaling plaques, 2) Invasive: Lesion often nodular and ulcerated | Excision (usually curative) | |
| Basal Cell Carcinoma | 1) Most common skin tumor, 2) slow growing w/ rare metastasis, 3) Sun exposed skin | Cords and islands of "basophilic" cells | 1) Pearly papule with telangectasia, 2) large tumors may ulcerate | Excision curative | |||
| Dermatofibroma (benign fibrous histiocytoma) | 1) Benign, 2) legs of young-middle aged women 3) antecedant trauma history | Fibroblast infiltration into dermis w/ epidermal hyperplasia | Firm tan to brown papule | ||||
| Acute Inflammatory Dermatoses | |||||||
| Mastocytosis | 1) Typically adults, 2) Poor prognosis | Systemic mastocytosis (increased mast cell in skin and organs) | 1) Mast cell granule release (histamine & heparin)= Pruritis, flushing, GI and nasal bleed (rare), Bone pain, 2) Dariers sign - rubbing induced erythema and edema | Variable histo from subtle dermal mast cell (spindle) increase to heavy round mast cell increase in upper dermis | round to oval, red/brown, non-scaling papules and plaques | ||
| 1) Most common type, 2) typically kids | Uticaria pigmentosa (localized to skin) | ||||||
| 1) Good prognosis | Mastocytoma (solitary cutaneous lesion) | ||||||
| Urticaria | 1) Typically 20-40yo (but all ages), 2) transient lesions resolve in 1-3 days, 3) Stimuli: pollens, food, drugs, ect. | 1) MECH: IgE mediated mast cell degranulation (Type I hypersensitivity) results in microvascular permeability and intersitial edema, 2) Hereditary angioneurotic edema (face) - C1 esterase def = uncontrolled complement activation | Normal looking biopsy w/ superficial dermal edema and dilated vessels | erythematous, edematous, circular plaques w/ normal epithelial surface | |||
| Eczema | 1) Types: Contact dermatitis (poison ivy), atopic dermatitis, drug-related eczematous, photoeczematous, primary irritant dermatitis | MECH: Type IV hypersensitivity (Langerhans cells process antigen, present to naïve CD4 T-cells. Memory T cells release cytokines stimulating inflammatory response) | Edematous epidermis with superficial dermal perivascular lymphocytic infiltrate | Red, papulovesicular, oozing, crusted lesions | atopic | irritant | |
| Erythema multiforme | 1) Self limited, 2) Stevens-Johnsons and toxic epidermal necrolysis (same process) | 1) MECH: Hypersensitivity to infection or drugs (CTL kill epidermal cells), 2) ASSN: Infections (HSV, mycoplasma), Drugs (sulfonamides, pen, barbs), Malignancy (carcinoma, lymphoma), Collagen vascular dx (SLE, dermatomyositis) | Target lesions (central necrosis w/ rim of pervenular inflammation) symmetrically on extremities | Lymphoyctes migrating from perivascular dermis to epidermis and killing keratinocytes | Targetoid lesions (characteristic, but many presentations) | ||
| Stevens-Johnson Syndrome | Erosion and crusting of mucosal surfaces casued by sulfonamide antibiotics | major = mucous membranes; minor = other | EM major | ||||
| Toxic epidermal necrolysis | Diffuse necrosis and sloughing of cutaneous and mucosal surfacs | Sloughing of entire epidermis | |||||
| Chronic Inflammatory Dermatoses | |||||||
| Psoriasis | 1) common on elbows, knee, scalp, lumbsacral, glans, interglueal cleft | 1) MECH: Sensitized T cells secrete cytokine (IL-10, TNF-a, IL-8) and growth factors resulting in increased cell turnover, vascular proliferation, and inflammation., 2) ASSN: Arthritis, myopathy, enteropathy, spondylitic heart disease, & AIDS | Epidermal hyperplasia, parakeratotic scales, and minute microabscesses of PMN within superficial epidermis | 1) well-demarcated, pink plaque with loose silver scales, 2) Oil-slick nail discoloration, 3) nail pitting | |||
| Lichen planus | 1) Self limited (1-2yr) | 1) MECH: Unknown, theory = antigen stimulated cell-mediated cytoxic rxn at basal level | Bandlike infiltrate of lymphocytes at dermal-epidermal jnct with pointed rete ridges | 1) Pruritic, purple, polygonal papules which may coalesce to form plaques, 2) symmetric | |||
| Discoid Lupus Erythematosus | 1) Localized cutaneous form of lupus (>33% SLE px develop DLE), 2) worse in sun-exposed skin | Perivascular lymphocytic infiltrate | Atrophic epidermis | 1) Malar erythema (systemic), 2) plaques with hypopigmented center and hyperpigmented periphery | |||
| Blistering Dermatoses | |||||||
| Pemphigus vulgaris | 1) uncommon, 2) M=F, 3) middle aged to elderly, 4) Location: scalp, face, axilla, groin, trunk | 1) MECH: Type II Hypersensitivity w/ anti-desmoglein IgG (intercellular desmosomal attachment loss), 2) Mixed inflammation | IF: "fish net" | Suprabasal acantholysis | Flaccid vessicles which rupture resulting in shallow erosions w/ crust | ||
| Bullous Pemphigoid | 1) Elderly, 2) Location: thighs, forearm flexor surf, axilla, groin, lower ab, and oral (30%) | 1) MECH: Type II hypersensitivity anti-pemphigoid antigen IgG (lamina lucida, bm zone, and hemidesmosome protein), 2) Eosinophils | IF: bm deposition | Subepidermal nonacantholytic blister | Tense bullae filled w/ clear fluid | ||
| Dermatitis Herpetiformis | 1) 30-40yo, 2) M>F, 3) Location: extensor, elbows, knees, upper back, buttock, 4) ASSN: celiac disease | 1) MECH: anti-gluten IgA (Gut B cell Ab cross reacts with transglutaminase a component of anchoring fibrils), 2) PMN inflammation | IF: IgA deposits at dermal papillae tips | PMN microabscesses in dermal papilale | Pruritic grouped vesicles | ||
| Epidermolysis bullosa aquisita | 1) Usually adults (any age), 2) Location: trauma-prone surfaces w/ variable mucous membrane involvement | 1) MECH: anti-collagen VII Ab (anchoring fibrils), 2) No inflammation | IF: Linear BM | Non inflammatory subepidermal blister | Flexural crease bullae | ||
| Inflammatory Dermatoses: Viral | |||||||
| Verrucae vulgaris | 1) Most common, 2) Location: Hands | 1) Anogenital warts (HPV 6 & 11), 2) Dysplasia (HPV 16), 3) Bowenoid papulosis (HPV 16; genital lesions appear as SCCIS but spontaneously regress), 4) Epidermodysplasia verruciformis (HPV 5 & 8: muliple flat warts which may evolve to SCC) | Large papillomatous projections. Hyperkeratosis w/ parakeratosis. Capillary loops in each projection. | Epidermal hyperplasia with atypia and keratohyaline granules | Grey papule with rough surface | ||
| Verruca Plana | 1) Location: face and hands | Tan slightly elevated smooth papules | The virus is in the epidermis around the warts (so must freeze a border) | ||||
| Verruca plantaris | 1) Location: palm and soles | Rough scaly lesions | |||||
| Condyloma accuminatum | 1) Location: genital and perianular warts | Cauliflower masses | |||||
| Molluscum contagiosum | 1) children and young adults, 2) self-lmited | 1) MECH: Pox virus spread through autoinnoculation | Endophytic epidermal prolif w/ large eosinophilic inclusions (virion) protruding out of invagination | umbilicated papules (central depression) | |||
| Herpes Simplex Virus | 1) HSV 1 & 2 | Intraepidermal ballooning | Cowdery A bodies | ||||
| Inflammatory Dermatoses: Bacterial | |||||||
| Staphlococcal scalded skin syndrome | 1) pre-existing infection focal cutaneous, 2) conjucntivits prior to rash, 3) most common in chldren (adults w/ immuno/renal compromise), 4) post-nasopharynx/skin staph infection | 1) MECH: Staph A exfoliative toxin (serine protease cleaves desmoglein 1 in desmosome) | Nikolsky's sign (push on skin gets extension of blister) | 1) intraepidermal vesicle in granular layer, 2) IF neg | Sunburn-like rash not involving mucuos membrane (SJ diff) w/ bullae and large desquamation | 1) antibiotics, 2) heals 1-2wk w/o scarring | |
| Impetigo (pyoderma) | 1) children, 2) highly contagious superficial skin infection | 1) MECH: Focal SSSS, 2) Staph aureus and streptococcus disease causing superficial skin infection | Focal bullae | ||||
| Ecthyma | Presentations: 1) lower extremeties of children, 2) neglected elderly, 3) lymphedema of limbs, 4) Immunocompromised | 1) MECH: SSSS extending into dermis (ulcer) | Ulcerated round lesion with peripheraly erythema | ||||
| Erysipelas | 1) ASSN: abrupt fever, chills, malaise, nausea onset | 1) MECH: Dermis infection w/ significant lymphatic involvemnet by Streptococcus pyogenes | 1) Spongiotic epidermis, 2) Edematous dermis, 3) PMN infiltrate, 4) dlated lymphatics | Well demarcated erythemaous and indurated lesion | |||
| Cellulitis | 1) Following skin abrasion | 1) MECH: Deep dermis and subcutaneous tissue infection, 2) S. pyogenes or S. aureus | fever, chills, malaise, warm, tender, erythematous lesion which is indefined with non-palpable borders | 1) Dermal infiltrate of PMN and lymphocytes, 2) edema & lymphatic dilation, 3) Gram stain positive | erythematous ildefined lesion w/ non-palpable borders | ||
| Leprosy | 1) Incubation months to years (5yr ave.), 2) Viable 7 days in dried secretions (viable), 3) Armadillos | 1) Mycobacterium leprae w/ 3 forms: Indeterminate, tuberculoid, lepromatous, 2) MECH: CMI determines disease form (intact = tuberculoid, depressed = lepromatous) | Tuberculoid gross: Patches w/ erythematous periphery and bland center | Tuberculoid: 1) Non-caseating granulomas w/ multinucleation, 2) lymphocytic infiltrate, 3) NO organisms | Lepromatous gross: | Lepromatous histo: 1) dense mac infiltrate, 2) Neurovascular bundle involvement, 3) Fite stain shows organisms | |
| Dermatophyte | |||||||
| Dermatophyte | Location based name: 1) Tinea versicolor (hypopigmented macules on trunk; Malassezia furfur - yeast), 2) Tinea capitis (head), 3) Tinea barbae (beard), 4) Tinea corporis (body), 5) Tinea pedis (feet), 6) Onychomycosis (nail) | 1) Stratum corneum fungal infection, 2) GROSS: Diffuse erythema,, scaling, circinate w/ an expanding border, 3) HISTO: slight to moderate dermis inflammation (PMN) + spongy epi + hyperkeratosis + PAS | Tinea corporis (pustule due to PMN migration) | Tinea capitis (follicle w/ hairshaft filled w/ fungus) | |||
| Inflammatory Dermatoses: Parasitic | |||||||
| Scabies | 1) Presentation: Papulovesicular (most common), Nodules, Crusted (immunosuppressed), 2) Location: interdigital folds, palms, fingers, wrists | Biopsy of immunosuppressed with scabies | Crust | ||||
| Nevoid basal cell carcinoma syndrome | 1) AD, 2) PTCH, | 1) PTCH gene product couples w/ smoothened. In absence of SHH the PTCH stays coupled and smoothened in inactive. SSH released smoothen resulting in gene expression w/ unregulated cell division , 2) two-hit hypothesis | |||||
| Neurofibromatosis I | |||||||
| Neurofibromatosis II | |||||||
| Mueir-Torre | 1) AD, 2) mismatch repair defect | ||||||