Step 2 review: derm

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  1. Type 1 sensitivity
    • anaphylactic and atopic
    • antigen cross-links IgE on presensitized mast cells
    • examples- anaphylaxis, asthma, urticarial drug reaction, local wheal and flare
  2. Type 2 hypersensitivity
    • cytotoxic
    • IgM and IgG + complement lead to MAC -> lysis or phagocytosis
    • examples- autoimmune hemolytic anemia, Rh disease, Goodpasture's, rheumatic fever
  3. Type 3 hypersensitivity
    • 1. Immune complex: antigen-antibody complement
    • examples- polyarteritis nodosa, glomerulonephritides, SLE, RA
    • 2. Serum sickness: antibodies to proteins produced --> immune complex forms fix complement
    • fever, urticaria, arthralgia, proteinuria, lymphadenopathy 5-10d after exposure
    • 3. Arthus reaction: local subacute reaction. Intradermal injection of antigen --> Ag-Ab complexes form
    • examples- hypersensitivity pneumonitis, thermophilic actinomycetes
  4. Type 4 hypersensitivity
    • delayed (cell-mediated) type: sensitized T cells release lymphokines
    • example- TB skin test, transplant rejection, conact dermatitis
  5. Seborrheic dermatitis: causative agent, population
    • Pityrosporum ovale
    • infants- diaper rash, "cradle cap"
    • young person- suspect HIV
  6. Psoriasis: physical features, diagnosis
    • psoriatic nails- pitting, "oil spots," onycholysis
    • Koebner's phenomenon- provoked by local irritation
    • strep infx can trigger guttate psoriasis, meds (beta blocker, Li, ACEi) can induce
    • "sausage digits"; Auspitz sign; on histology Munro's microabscess
  7. Image Upload 1
    • Erythema Multiforme
    • triggers- HSV infx of lip, drugs (sulfa, phenytoin, barbiturates, PCN, NSAIDs), mycoplasmal infx
    • target appearance
    • palms and soles affected
    • could have systemic symptoms
    • if severe, can lead to TEN or SJS
    • symptomatic treatment
  8. SJS
    • SJS: epidermal separation < 10% BSA. degeneration of basal layer of epidermis
    • TEN: >30% BSA. full-thickness eosinophilic epidermal necrosis
    • flulike prodrome, erythema multiforme, associated with new drugs (pheytoin, carbamazepine, quinolone, cephalosporin, allopurinol, corticosteroids, NSAIDs)
    • + Nikolsky's sign
    • histology- degeneration of basal layer epidermis, perivascular mononuclear infiltrate
  9. Staphylococcal scalded skin syndrome
    • children < 6 yrs of age
    • infectious etiology
    • lose widespread sheets of skin, superficial damage
  10. Image Upload 2
    • Erythema nodosum
    • panniculitis triggered by infection (strep, coccidioides, yerinia, TB), drug rxn, chronic iflammatory dz (sarcoid, Crohn's, UC, Behcet's)
    • painful, erythematus nodules on lower legs turns brown or gray
    • may have false +VDRL
  11. Pemphigus vulgaris: characteristics, tx
    • age 40-60
    • intraepidermal blister, widespread painful erosions
    • antibodies against desmoglein
    • mucous membrane --> skin involvement
    • dx- clinical picture, + Nikolsky's sign, skin bx with immunofluorescence (bx shows acantholysis)
    • tx- systemic corticosteroids + steroid sparing agents (mycophenolate mofetil, azathioprine)
  12. Bullous pephigoid: characteristics, tx
    • acquired blistering disease
    • age 60-80
    • separation at epidermal basement membrane. blisters are stable
    • - Nikolsky's sign
    • mucous membranes less involved than pemphigus
    • dx- clinical picture
    • tx- systemic corticosteroids
  13. Dermatitis herpetiformis: chacteristic, tx
    • pruritic papules and vesicles on elbows, knees, buttocks, neck, scalp
    • Granular IgA on dermal papillae
    • associated with celiac disease
    • tx- dapsone, gluten free diet
  14. HSV
    • HSV-1 oral, HSV-2 genital
    • cluster of vesicles on erythematous base
    • dx- clinical picture, multinucleated giant cells on Tzanck smear
    • tx- oral or IV acyclovir
  15. VZV
    • varicella: prurpitic lesion red macules --> grouped vesicles "dewdrop on rose petal"
    • at any time all stages of lesions over body. palms, soles spared
    • zoster: lesions along dermatome
    • preceded by intense local pain
    • older pts may have postherpetic neuralgia
    • tx- systemic acyclovir, pain control
  16. Molluscum contagiosum
    • poxvirus causes tiny waxy papules with central umbilication
    • in children- trunk, extremities, face
    • in adults- genitalia, perineal region. if large, think AIDS
    • dx- clinical picture, giemsa or wright's stain shows large inclusion or molluscum bodies
  17. Impetigo: causative agents, types
    • group A strep, staph
    • common type: pustules, honey-colored crusts usually on face
    • bullous type: acral, large stable blisters. almost always caused by S.aureus- can evolve into SSSS
    • tx- methicillin, oxacillin, nafcillin
  18. Erysipelas
    • group A strep superficial cellulitis
    • small red patch on cheek --> painful raised, shiny plaque (+/- vesicles)
    • often history of trauma or pharyngitis
    • tx- dicloxacillin, cephalexin or clinda
  19. Erythrasma
    • Corynebacterium
    • browinsh-red patch with fine scale, appear in major skin folds
    • dx- Wood's light shows coral-red fluorescence, GPR
    • tx- erythromycin
  20. Scarlet fever
    • S. pyogenes
    • strawberry tongue
    • tx- PCN
  21. Nec Fasciitis
    • deep infection along fascial plane- pain --> anesthesia
    • S.pyogenes, Clostridium perfringens
    • tissue necrosis, putrid discharge, bullae, severe pain, gas production
    • dx- radiographs or CT, bx
    • tx- surgical emergency. if strep, PCN G (clindamycin 2nd line). metronidazole or 3G ceph for anaerobe
  22. Tinea Versicolor
    • Malassezia furfur
    • risk fx- humid, sweaty conditions, oily skin, Cushing's syndrome, immunosuppression
    • dx- clinical picture, KOH shows "spaghetti and meatballs" pattern
    • tx- topical selenium sulfide
  23. Gangrene: subtypes
    • dry: insufficient blood flow, usually atherosclerosis
    • wet: bac infx
    • gas: Clostridium perfringens. usually at site of recent injury/surgery- medical emergency
    • tx- surgical debridement. hyperbaric O2 for gas gangrene
  24. Lichen Planus
    • chronic inflammatory dermatosis (skin and MM), can be induced by drugs, HCV infx
    • purple, polygonal papule, pruritic, penile
    • Wickham's striae, Koebner's phenomenon
    • dx- histology
    • tx- topical corticosteroids for mild dz
  25. Toxic shock syndrome
    • inflammatory response c fever, rash, hypotension, constitutional syndromes
    • trunk --> extremities
    • need 3+ organ involvement
  26. Image Upload 3
    • Pityriasis Rosea
    • HHV 6 or 7
    • hearld patch --> multiple symmetric papules along skin lines with "cigarette paper" scale. "Christmas tree pattern"usually on trunk
  27. Dermatophyte: causative organisms, treatment
    • Microsporum, Trichophyton, Epidermophyton
    • risk fx- pets, DM, dec peripheral circulation, immune compromise, athletics
    • tx- topical or systemic antifungals. tinea capitis must be treated with systemic drugs
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Step 2 review: derm

derm review for step 2
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