Melasma pathogenesis involves which interaction that drives epidermal hyperpigmentation beyond simple sun exposure?

• A Stem cell factor (SCF)/c-Kit and endothelin-1 (ET-1) from keratinocytes activating melanocytes ✓
• B IL-17A from T-cells directly stimulating melanocytes
• C Autoimmune destruction of surrounding melanocytes causing rebound hyperpigmentation
• D TGF-beta-mediated dermal fibrosis stimulating melanogenesis

Explanation

In melasma, UV exposure induces keratinocytes to secrete SCF (stem cell factor), endothelin-1, and prostaglandins, which activate c-Kit receptor on melanocytes leading to increased melanogenesis and dendricity. Additionally, hormonal factors (estrogen/progesterone activate ERα in melanocytes) and vascular changes (increased VEGF, dermal neovascularization) contribute. This explains why sun protection alone is insufficient and why oral tranexamic acid (which inhibits plasminogen activator-mediated prostaglandin release) is effective.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.