Applied Dermatology: Therapy and Procedures
Therapeutics
Applied questions test practical decision-making. Know topical corticosteroid potency classes and site-specific selection (low potency for face/flexures, high potency for palms/soles). Understand calcineurin inhibitors, vitamin D analogs, retinoids, and their monitoring. Systemic therapy requires familiarity with methotrexate (LFTs, CBC, pregnancy avoidance), cyclosporine (renal, BP), azathioprine (TPMT), and biologics (infection screening, TB before anti-TNF).
Procedures
Cryotherapy, electrodesiccation, excision with margins, and Mohs micrographic surgery each have indications. Mohs suits high-risk basal cell carcinoma on the face and recurrent tumors. Know suture selection, wound care basics, and when to refer.
Phototherapy and lasers
NBUVB for psoriasis and vitiligo; PUVA carries cumulative risk. Laser principles: selective photothermolysis-target chromophore, wavelength, and pulse duration. Vascular lasers target oxyhemoglobin; pigment lasers target melanin.
Traps
Questions often test contraindications (isotretinoin and pregnancy, methotrexate and pregnancy, cyclosporine and uncontrolled hypertension). Another trap is confusing prophylactic with therapeutic regimens, or choosing a procedure that violates margin principles for melanoma.
Rule of thumb
Match potency to site and thickness: thin skin and flexures get low potency; thick palms, soles, and plaques get high potency or intralesional steroid. For melanoma, never compromise margins for cosmesis-excision with appropriate margins first, reconstruction second.
Worked example
A facial recurrent basal cell carcinoma in a young patient: Mohs is preferred for tissue conservation and margin control. If the question specifies a small primary superficial lesion on the trunk, cryotherapy or curettage may be acceptable.