1. Primary Lesions
   1. Macule
      1. flat lesion <1cm
      2. Telangiectasia, Petechia, Nevus
   2. Patch
      1. flat lesion >1cm
      2. Purpura, Hemangioma, Cafe au lait, Vitiligo
   3. Papule
      1. elevated <1cm
      2. Halo nevus, Seborrheic keratoses, Pustule
   4. Plaque
      1. elevated >1cm
      2. Psoriasis, Urticaria
   5. Nodule
      1. rounded <1cm
      2. Pyogenic granulomas, ulceration, erosion
   6. Tumor
      1. rounded >1cm
      2. Large seborrheic keratosis, keloid
   7. Vesicle
      1. blister <1cm
      2. Contact Dermititis
   8. Bulla
      1. blister >1cm
      2. Herpes Zoster, Hand-Food-Mouth
2. Skin
   1. Immune
      1. TH1 and TH2
         1. Leprosy
            1. Lepromatous
            2. Tuberculoid
      2. TH1
         1. Psoriasis
            1. Plaque
            2. Guttate
            3. Erythrodermic
            4. Pustular
            5. Psoriatic Arthritis
            6. Psoriatic Nails
         2. Seborrheic Dermatitis
         3. Lichen Planus
         4. Vitiligo
            1. Piebalism
            2. Tuberous Sclerosis
         5. Alopecia Areata
      3. TH2
         1. Atopic Dermatitis
         2. Contact Dermatitis
         3. Eczema
      4. Other
         1. Sarcoidosis
         2. Pemphigus Foliaceus
         3. Pemphigus Vulgaris
         4. Bullous Pemphigoid
         5. Dermatitis Herpetiformis
         6. Kawasaki's Disease
         7. Erythema toxicum neonatorum
   2. Infectious
      1. Bacteria
         1. Acne
         2. Folliculitis
         3. Furuncle
         4. Carbuncle
         5. Abscess
         6. Impetigo
            1. Erysipelas
         7. Cellulitis
         8. Gangrene
            1. Dry Gangrene
            2. Moist Gangrene
            3. Necrotizing Fasciitis
         9. Meningococcemia
         10. Typhoid Fever
         11. Staph Scalded Skin Syndrome
         12. Bullous Impetigo
         13. Scarlet Fever
         14. Toxic Shock Syndrome
         15. Rocky Mountain Spotted Fever
      2. Fungal
         1. Candida
         2. Dermatophytes
         3. Tinea capitis
         4. Tinea versicolor
         5. Bullous Tinea Pedis
         6. Seborrheic Dermatitis
      3. Viral
         1. HPV
            1. Condylomata acuminata
         2. HSV
         3. VZV
         4. Molluscum contagiosum
         5. HIV
            1. Thrush
            2. Leukoplakia
         6. HHV6,7,8
            1. Pityriasis Rosea
         7. Measles
         8. Rubella
         9. Chickenpox
         10. Roseola infantum
         11. Pityriasis Rosea
         12. Hand-foot-and-mouth
         13. Herpangina
         14. Erythema infectiosum
         15. Mononucleosis
      4. Other
         1. Lyme
         2. Syphilis
         3. Pediculosis
            1. Capitis
            2. Corporis
            3. Pubis
         4. Scabies
            1. Nodular Scabies
            2. Crusted Scabies
         5. DDx of Penis Ulceration
            1. HSV
            2. Syphilis
            3. Chancroid
            4. Lymphogranuloma Venereum
            5. Granuloma inguinale
3. Systemic
   1. Immune
      1. Reiter's Syndrome
      2. Vasculitis
      3. Scleroderma
         1. Morphea
         2. CREST
         3. Progressive Systemic Sclerosis
      4. Lupus
         1. SLE
         2. SCLE
         3. Discoid Lupus
         4. Lupus Panniculitis
      5. Dermatomyositis
      6. Poikiloderma
      7. Rheumatoid Arthritis
   2. Infectious
      1. Lyme
      2. Rheumatic Fever
   3. Nutritional
      1. A: Phrynoderma
      2. C: Scurvy
      3. K: Purpura
      4. B1: Beriberi
      5. B2/Riboflavin
      6. B3: Pellagra
      7. B12: Anemia
      8. Iron: Anemia, Koilonychia
      9. Zinc: Acrodermatitis Enteropathica
      10. Kwashiorkor
      11. Marasmus
      12. Vitamin D Metabolism
   4. Endocrine
      1. Hyperthryroidism
      2. Hypothyroidism
      3. Cushing's Disease
      4. Addison's Disease
      5. Diabetes Mellitus
      6. Testosterone Excess
      7. Myxedema
      8. Acanthosis Nigricans
      9. Hyperpigmentation
      10. Acne with Hirsutism
   5. Congenital
      1. Epidermolysis Bullosa
      2. Ehler's Danlos Syndrome
      3. Marfan's Syndrome
      4. Pseudoxanthoma Elasticum
      5. Ichthyosis Vulgaris
      6. Neurofibromatosis
   6. Malignancy
      1. Glucogonoma
      2. Lung CA
      3. GI CA
      4. Hodgkin's Lymphoma
      5. CTCL
      6. Multiple Myeloma & Amyloidosis
      7. Ovarian CA
      8. Breast CA
      9. Necrolytic Migratory Erythema
      10. Erythena Gyratum Repens
      11. Acanthosis Nigricans & Leser-Trelat
      12. Pruritis
      13. Erythroderma
      14. Purpura
      15. Dermatomyositis
      16. Peau d'Orange
4. Other
   1. Drug Hypersensitivity
      1. Type I
         1. Anaphylactic
            1. Angioedema
            2. Anaphylaxis
            3. Red Man Syndrome
            4. Urticaria
      2. Type II
         1. Cytotoxic
            1. Drug-induced SLE
            2. Drug-induced subacute cutaneous lupus (SCLE)
            3. Heparin Necrosis
            4. Autoimmune Thrombocytopenia
            5. Drug-induced Blistering Disorders
            6. Pemphigus Vulgaris
            7. Linear IgA disease
            8. Bullous Pemphigoid
      3. Type III
         1. Immune Complex
            1. Serum Sickness
            2. Leukocytoclastic Vasculitis
      4. Type IV
         1. Delayed
            1. Allergic Contant Dermatitis
            2. Morbilliform Rash
            3. Fixed Drug Eruption
            4. Erythema Multiforme
            5. Stevens Johnson Syndrome
            6. Toxic Epidermal Necrolysis
   2. Misc 1
      1. Liver Failure
         1. Purpura, spider angioma, jaundice, palmar erythema, caput madusa
      2. Renal Failure
         1. Pruritis
      3. Nail Conditions
         1. Beau's Lines
         2. Terry's Lines
         3. Lindsay's Lines
         4. Muehrke's Lines
         5. Mee's Lines
         6. Onychogryphosis
      4. Erythema Nodosum
      5. Hyperhydrosis
      6. Hidradenitis Suppurative
      7. Miliaria
   3. Misc 2
      1. Alopecia
         1. Scarring
         2. Non-Scarring
      2. Burns
         1. Chemical
         2. Electrical
         3. Inhalational
         4. Circumferential
         5. Sunburn
         6. Burn Wound Sepsis
      3. Ulcers
         1. Stage I - IV
      4. Senile Purpura
5. Skin Tumors
   1. Benign
      1. Lumps and bumps
         1. Seborrheic Keratosis
         2. Sebaceous Hyperplasia
         3. Acrochordon
         4. Hemangiomas
            1. Cherry Hemangioma
            2. Capillary Hemangioma
            3. Disseminated Neonatal Hemangioma
         5. Dermatofibroma
         6. Venous Malformation
            1. Port Wine Stain
            2. Nevus Flammeus
         7. Epidermoid Cyst
         8. Lipoma
      2. Pigmented macules
         1. Melasma
         2. Post-inflammatory Hyperpigmentation
         3. Ephilide
         4. Lentigo
            1. Solar Lentigo
         5. Cafe-au-lait Macule
         6. Dermal Hypermelanosis
         7. Nevus of Ota
   2. Malignant
      1. at risk
         1. Actinic Keratosis
         2. Melanocytic Nevi
            1. Intradermal
            2. Junctional
            3. Compound
      2. malignant
         1. Basal Cell Carcinoma
         2. Squamous Cell Carcinoma
            1. Bowen's Disease
         3. Cutaneous T-cell Lymphoma (Mycosis Fungoides)
            1. Sezary Syndrome
         4. Kaposi's Sarcoma
         5. Melanoma