Traumatic anserine folliculosis (TAF) is a rare, under-recognized dermatological condition caused by repeated friction or pressure. This leads to grouped follicular papules with a rough, sandpaper-like texture, most commonly on the face or neck. It primarily affects adolescents and young adults, with pathogenesis linked to mechanical irritation causing follicular hyperkeratosis and keratin plug formation. We report the case of a young male who developed hyperpigmented follicular papules on his left cheek with a history of resting his cheek on his palm. Clinical evaluation confirmed TAF, and treatment with topical retinoids and keratolytics, along with avoidance of friction, led to marked improvement after nine months. The diagnosis of TAF is clinical and relies on recognizing the frictional history and characteristic lesions, distinguishing it from conditions like keratosis pilaris (KP) and lichen spinulosus. Management centers on educating patients, eliminating trauma, and using topical retinoids or keratolytics, with generally excellent outcomes when identified and treated early.
Natural keratin fibers, such as wool, possess a complex hierarchical structure that governs their mechanical properties and surface energy. However, the extent to which these characteristics are influenced by combined contributions of structural variations (e.g., fiber diameter, intermediate filament (IF) packing) and chemical composition (e.g., disulfide bond density) remains poorly understood. In this study, we investigate wool fibers from five sheep breeds (Merino, Polwarth, Cheviot, Eider, and Devon) to elucidate how these factors influence viscoelasticity and surface interactions. Using a multimodal approach integrating interfacial and bulk characterization methods, including inverse gas chromatography (IGC), atomic force microscopy-infrared spectroscopy (AFM-IR), X-ray photoelectron spectroscopy (XPS), uniaxial tensile testing, and synchrotron small-angle X-ray scattering (SAXS), we show that the nanometer-thick 18-methyleicosanoic acid (18-MEA) layer is consistently present across all wool types and plays a key role in governing hydrophobicity and surface heterogeneity. A controlled isothermal treatment at 200 °C, designed to cleave disulfide bonds, results in a nearly 40% reduction in specific surface area across all fiber types, accompanied by a significant decrease in tensile strength and 80% reduction in elongation at break for Merino and Devon wool, but limited influence on the mechanical properties of Eider fibers. Furthermore, rate-dependent tensile testing within the elastic regime reveals distinct viscoelastic responses among the fiber types, suggesting that the sulfur-rich protein matrix surrounding IFs and its structure contribute actively to stress partitioning. Altogether, when combined with conclusions from SAXS measurements of IF spacing, our work offers compelling insights into the role of the keratin-associated protein (KAP) matrix in shaping wool fiber mechanics. Differences in mechanical behavior among wool types, despite similar IF spacing or sulfur content, highlight the importance of matrix composition and cross-linking density, suggesting that the molecular architecture of the KAP network may be a dominant factor in determining fiber performance.
Traumatic anserine folliculosis (TAF) is a rare, under-recognized dermatological condition caused by repeated friction or pressure. This leads to grouped follicular papules with a rough, sandpaper-like texture, most commonly on the face or neck. It primarily affects adolescents and young adults, with pathogenesis linked to mechanical irritation causing follicular hyperkeratosis and keratin plug formation. We report the case of a young male who developed hyperpigmented follicular papules on his left cheek with a history of resting his cheek on his palm. Clinical evaluation confirmed TAF, and treatment with topical retinoids and keratolytics, along with avoidance of friction, led to marked improvement after nine months. The diagnosis of TAF is clinical and relies on recognizing the frictional history and characteristic lesions, distinguishing it from conditions like keratosis pilaris (KP) and lichen spinulosus. Management centers on educating patients, eliminating trauma, and using topical retinoids or keratolytics, with generally excellent outcomes when identified and treated early.
Natural keratin fibers, such as wool, possess a complex hierarchical structure that governs their mechanical properties and surface energy. However, the extent to which these characteristics are influenced by combined contributions of structural variations (e.g., fiber diameter, intermediate filament (IF) packing) and chemical composition (e.g., disulfide bond density) remains poorly understood. In this study, we investigate wool fibers from five sheep breeds (Merino, Polwarth, Cheviot, Eider, and Devon) to elucidate how these factors influence viscoelasticity and surface interactions. Using a multimodal approach integrating interfacial and bulk characterization methods, including inverse gas chromatography (IGC), atomic force microscopy-infrared spectroscopy (AFM-IR), X-ray photoelectron spectroscopy (XPS), uniaxial tensile testing, and synchrotron small-angle X-ray scattering (SAXS), we show that the nanometer-thick 18-methyleicosanoic acid (18-MEA) layer is consistently present across all wool types and plays a key role in governing hydrophobicity and surface heterogeneity. A controlled isothermal treatment at 200 °C, designed to cleave disulfide bonds, results in a nearly 40% reduction in specific surface area across all fiber types, accompanied by a significant decrease in tensile strength and 80% reduction in elongation at break for Merino and Devon wool, but limited influence on the mechanical properties of Eider fibers. Furthermore, rate-dependent tensile testing within the elastic regime reveals distinct viscoelastic responses among the fiber types, suggesting that the sulfur-rich protein matrix surrounding IFs and its structure contribute actively to stress partitioning. Altogether, when combined with conclusions from SAXS measurements of IF spacing, our work offers compelling insights into the role of the keratin-associated protein (KAP) matrix in shaping wool fiber mechanics. Differences in mechanical behavior among wool types, despite similar IF spacing or sulfur content, highlight the importance of matrix composition and cross-linking density, suggesting that the molecular architecture of the KAP network may be a dominant factor in determining fiber performance.
Rxiv cytoskeleton
Rxiv mechanobio