The Dark Side of Gefitinib: Reflectance Confocal Microscopy Applied to Hair Hyperpigmentation

Drug-Induced Pigmentation: A Review

Drug-induced pigmentation (DIP) is estimated to account for 20% of all cases of acquired hyperpigmentation. Over 50 agents have been implicated, including antibiotics, antimalarials, antiretrovirals, antipsychotics, prostaglandin analogs, heavy metals, and chemotherapeutic agents. The skin, mucosal surfaces, nails, and hair can all be affected, with the color, distribution, onset, and duration of pigmentation varying between offending agents. Both a thorough physical examination and medication history are necessary to determine the offending agent. In terms of mechanism, DIP occurs most frequently through the accumulation of melanin within the dermis but also by drug accumulation, pigment synthesis, and iron deposition. Photoprotection, including applying a broad-spectrum sunscreen, wearing photoprotective clothing, and seeking shade, plays an important role in the prevention of exacerbation of DIP. Multiple lasers, including the picosecond alexandrite, Q-switched Nd:YAG, Q-switched alexandrite, and Q-switched ruby lasers, have been successful in obtaining clearance of DIP. In this review, we examine the unique characteristics of each of the inciting agents in terms of incidence, clinical presentation, time to onset and resolution, and pathogenesis.

Effects of EGFR-TKI on epidermal melanin unit integrity: Therapeutic implications for hypopigmented skin disorders

Epidermal melanin unit integrity is crucial for skin homeostasis and pigmentation. Epidermal growth factor (EGF) receptor (EGFR) is a pivotal player in cell growth, wound healing, and maintaining skin homeostasis. However, its influence on skin pigmentation is relatively unexplored. This study investigates the impact and underlying mechanisms of EGFR inhibitors on skin pigmentation. We evaluated EGF and EGFR expression in various skin cells using quantitative real-time PCR, Western blot, and immunofluorescence. EGF and EGFR were predominantly expressed in epidermal keratinocytes, and treatment with the EGFR tyrosine kinase inhibitors (EGFR-TKIs) gefitinib and PD153035 significantly increased stem cell factor (SCF) and endothelin-1 (ET-1) expression in cultured keratinocytes. Enhanced melanocyte migration and proliferation were observed in co-culture, as evidenced by time-lapse live imaging and single-cell tracking assays. Furthermore, topical application of gefitinib to guinea pig dorsal skin induced increased pigmentation and demonstrated efficacy in mitigating rhododendrol-induced leukoderma. Suppression of EGF signaling indirectly enhanced skin pigmentation by upregulating SCF and ET-1 in epidermal keratinocytes. This novel mechanism highlights the pivotal role of EGF signaling in regulating skin pigmentation, and topical EGFR-TKI therapy at an appropriate dose may be a promising approach for depigmentation disorder management.

A systematic review on the lipid composition of human hair

Hair lipid composition varies by ethnic hair type and by hair layer. Lipids in the cuticle, cortex, and medulla of the hair shaft provide a protective barrier to environmental and chemical damage, prevent hair breakage and desorption, and affect the elastic and tensile properties of hair. The aim of this systematic review is to provide an overview of the lipid composition and ethnic differences of human hair, effects of external damage on lipid content and properties, and changes in hair lipid composition associated with disease states. PubMed/MEDLINE was searched up to March 2021 according to PRISMA guidelines for articles discussing the lipid content of human hair and effects of physical, chemical, or environmental damage, and disease. Fifty-nine articles investigating the lipid content of hair were included for review. Lipids affect fluid permeability, hydration, strength, and texture of ethnic hair fibers. Lipid loss is accelerated by hair-damaging treatments such as bleach, dye, perm, straightening, and surfactant use, and sun and aging processes, leading to dehydrated, breakable, disordered, and dull hair. Diseases including acne, alopecia, and breast, gastric, prostate, lung, and rectal cancers display elevated hair lipid levels. Lipids are vital in protection against damage and maintenance of healthy hair. Further studies are needed to investigate the effects of lipids on the structural properties of ethnic hair, and changes in hair lipid composition with various dermatologic and systemic diseases.