Disorders of the epidermis or epidermal appendages

**Definition:** This group incorporates skin disorders involving principally the epidermis, including abnormalities of keratinization and pigmentation, and the epidermal appendages, namely the hair follicular unit (hair, hair follicle, sebaceous gland, apocrine duct and apocrine gland), the eccrine sweat gland apparatus (eccrine duct and gland) and the nail apparatus.