Derm

1. Inflammatory Dermatoses

1. Atopic dermatitis – Chronic, pruritic, flexural distribution; elevated IgE

2. Contact dermatitis – Irritant (direct damage) vs. Allergic (type IV hypersensitivity)

3. Psoriasis – Well-demarcated silvery scales (plaques), Koebner phenomenon; guttate (post-Strep), pustular (steroid withdrawal)

4. Lichen planus – Purple, pruritic, flat-topped papules; Wickham striae (oral)

5. Seborrheic dermatitis – Greasy scales on scalp/face (dandruff, cradle cap); linked to Malassezia

6. Pityriasis rosea – Herald patch → Christmas tree rash; vs. secondary syphilis

7. Erythrasma – Coral-red fluorescence (Wood’s lamp); Corynebacterium minutissimum

2. Infectious Dermatology

8. Impetigo – Honey-colored crusts (S. aureus/S. pyogenes); bullous = S. aureus

9. Cellulitis (deep dermis/subQ) vs. Erysipelas (superficial, raised borders; S. pyogenes)

10. HSV-1/2 – Painful vesicles; Tzanck smear (multinucleated giant cells)

11. VZV – Chickenpox (dew on rose petal) vs. Shingles (dermatomal, postherpetic neuralgia)

12. Tinea infections – Corporis (ringworm), Capitis (scaling + alopecia; Microsporum/Trichophyton)

13. Folliculitis/Furuncle/Carbuncle – S. aureus (furuncle = boil; carbuncle = coalesced)

14. Scabies – Burrows, intense itch; permethrin treatment

15. Molluscum contagiosum – Umbilicated papules; poxvirus

16. Candidiasis – Satellite lesions, intertriginous (DM/antibiotics)

17. Erythema infectiosum – "Slapped cheek" (Parvovirus B19; aplastic crisis in sickle cell)

3. Autoimmune & Blistering Disorders

18. Pemphigus vulgaris – Nikolsky sign+, suprabasal blisters; anti-desmoglein 3

19. Bullous pemphigoid – Subepidermal blisters; linear IgG/C3 on BM

20. Dermatitis herpetiformis – IgA deposits; gluten-sensitive enteropathy

21. SLE – Malar rash (spares nasolabial folds), discoid lupus

22. Dermatomyositis – Heliotrope rash, Gottron’s papules; anti-Mi2

23. Epidermolysis bullosa – Trauma-induced blisters; genetic collagen defects

24. Linear IgA bullous dermatosis

4. Neoplastic & Premalignant Lesions

25. Actinic keratosis – Scaly, rough; precursor to SCC

26. SCC – Ulcerated nodule; risk in immunosuppression

27. BCC – Pearly papule, telangiectasia; least metastatic

28. Melanoma – ABCDE criteria; superficial spreading = most common

29. Mycosis fungoides – Patch → plaque → tumor; CD4+ T-cell lymphoma

30. Kaposi sarcoma – Purple plaques; HHV-8, HIV-associated

5. Vascular & Reactive Dermatoses

31. Erythema multiforme – Target lesions; HSV/mycoplasma triggers

32. SJS/TEN – Nikolsky sign+, mucosal involvement; drugs (sulfa, allopurinol)

33. HSP – Palpable purpura (IgA vasculitis); post-Strep, abdominal pain

34. Leukocytoclastic vasculitis – Small vessel vasculitis; palpable purpura

35. Pyoderma gangrenosum – Pathergy; IBD/RA association

36. Urticaria – IgE-mediated; wheals (mast cell degranulation)

37. Necrobiosis lipoidica – Yellow-brown plaques; pretibial, diabetic

6. Drug-Induced & Systemic Rashes

38. DRESS – Eosinophilia, organ involvement; anticonvulsants

39. Fixed drug eruption – Recurrent red/brown patches; sulfonamides

40. Acne vulgaris – Comedones; acneiform rash (steroids, EGFR inhibitors)

41. Erythema nodosum – Tender red nodules; sarcoidosis/IBD/Strep

42. Erythema migrans – Lyme disease (Borrelia burgdorferi); "bull's-eye"

43. Lichenoid drug eruption – Thiazides, antimalarials; mimics lichen planus

44. Serum sickness-like reaction – Cefaclor; immune complex-mediated

7. Nutritional & Metabolic

45. Pellagra – Niacin deficiency (3 D’s: Dermatitis, Diarrhea, Dementia)

46. Acanthosis nigricans – Velvety hyperpigmentation; insulin resistance

8. Key Signs & Associations

47. Darier’s sign – Urtication upon rubbing → mastocytosis

48. Nikolsky sign – Skin sloughing → Pemphigus vulgaris/TEN

49. Koebner phenomenon – Psoriasis, lichen planus, vitiligo