Differential Diagnoses

Question 1

Lesion : Brown Macule

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 1

Lesion : Brown Macule
- Infectious: -
- Inflammatory: Post-inflammatory, hyper-pigmentation
- Drug/Toxin: UV radiation, actinic/solar lentigo, freckle (ephelide)
- Miscellaneous: Congenital: café-au-lait spots, congenital nevus, epidermal/ junctional nevus. Neoplasia: lentigo maligna, MM, pigmented BCC
Other: melasma/chloasma (“mask of pregnancy”)

Question 2

Lesion : Discrete Red Papule

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 2

Lesion : Discrete Red Papule

• Infectious: Folliculitis, Furuncle, Scabies
• Inflammatory: Acne vulgaris, Lichen planus, Rosacea, Psoriasis, Urticaria
• Drug/Toxin: Bites/stings
• Miscellaneous: Vascular: hemangioma, pyogenic granuloma Other: dermatofibroma, milaria rubra

Question 3

Lesion : Red Scales

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 3

Lesion : Red Scales

• Infectious: Pityriasis rosea, Secondary syphilis, Tinea
• Inflammatory: Dermatitis (atopic, contact, nummular, seborrheic), Discoid lupus, Lichen planus, Psoriasis
• Drug/Toxin: Gold
• Miscellaneous: Neoplastic: mycosis fungoides

Question 4

Lesion : Vesicle

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 4

Lesion : Vesicle

• Infectious: Cat scratch disease, Impetigo, Viral: HSV, HZV, VZV, Molluscum, Coxsackie, Scabies
• Inflammatory: Acute contact dermatitis, Dyshidrotic eczema
• Drug/Toxin: -
• Miscellaneous:Other: dermatitis herpetiformis, porphyria cutanea tarda

Question 5

Lesion : Bulla

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 5

Lesion : Bulla

• Infectious: Bullous impetigo
• Inflammatory: Acute dermatitis EM, SJS, TEN, SLE
• Drug/Toxin:Fixed drug eruption
• Miscellaneous: Autoimmune: bullous pemphigoid, pemphigus vulgaris Other: dermatitis herpetiformis, porphyria cutanea tarda

Question 6

Lesion : Pustule

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 6

Lesion : Pustule

• Infectious: Candida, Dermatophyte, Impetigo, Sepsis, Varicella
• Inflammatory: Acne vulgaris, Rosacea, Dyshidrotic dermatitis, Pustular folliculitis, Pustular psoriasis
• Drug/Toxin: Acute generalized exanthematous pustulosis (usually secondary to drug reaction)
• Miscellaneous: Other: hidradenitis suppurativa

Question 7

Lesion : Oral Ulcer

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 7

Lesion : Oral Ulcer
- Infectious: Aspergillosis, CMV, Coxsackie, Cryptococcosis, HSV/HZV, HIV, TB, Syphilis
- Inflammatory: Allergic stomatitis, EM/SJS/TEN, Lichen planus, Seronegative arthropathies, SLE, Recurrent aphthous stomatitis, Behçet’s disease
- Drug/Toxin: Chemotherapy Radiation therapy
- Miscellaneous: Autoimmune: pemphigus vulgaris Congenital: XXY
Hematologic: sickle cell disease Neoplasia: BCC, SCC

Question 8

Lesion : Skin Ulcer

• Infectious
• Inflammatory
• Drug/Toxin
• Miscellaneous

Answer 8

Lesion : Skin Ulcer
- Infectious: Plague, Syphilis, TB, Tularemia
- Inflammatory: RA, SLE, vasculitis, UC (pyoderma gangrenosum)
- Drug/Toxin
- Miscellaneous: Autoimmune: necrobiosis lipoidica diabeticorum (e.g. DM) Congenital: XXY
Hematologic: sickle cell disease
Neoplasia: SCC
Vascular: arterial, neurotropic, pressure, venous, aphthous, leukoplakia, traumatic