When the skin ulcerates and the epidermis is stripped away (denuded), it's called:

The correct term for the process when the skin ulcerates and the epidermis is stripped away is desquamation. Desquamation refers specifically to the shedding or peeling of the outer layer of skin, which can occur due to various factors, including injury, infection, or certain skin conditions. When the epidermis is affected severely, such as in cases of ulceration, this process is characterized by the loss of the protective outer layer, leading to exposed skin and potential for further complications or infections.

Other options refer to different skin conditions or terms. Echinococcis is an infection caused by a parasite and does not relate to skin shedding. Hidradenitis suppurativa is a chronic skin condition marked by swollen lumps, often accompanied by pus, but does not describe the loss of epidermis. Erythema is a term that refers to redness of the skin, usually due to increased blood flow, and does not involve the actual desquamation or ulceration of skin. Understanding these distinctions helps clarify why desquamation is the accurate answer in this context.