A keratoma is a localized thickening of the skin caused by an accumulation of keratin, the protein that makes up the outer layer of the skin. It typically develops in response to repeated pressure, friction, or irritation, and can appear as a hard, raised area on the hands, feet, or other areas subject to mechanical stress. Keratomas are generally benign but may cause discomfort or pain, especially when located on weight-bearing surfaces.