What are the characteristics of 4th degree frostbite?

• A. Freezing deep to muscle, tendon, and bone
• B. Mottled skin
• C. Nonblanching cyanosis
• D. Dry, black, mummified eschar

Answer: (A)

Fourth-degree frostbite means the freezing extends beyond the skin into deep tissues—muscle, tendons, and even bone—causing nonviable tissue and a high risk of gangrene or amputation. That deep involvement is what distinguishes it from the other grades, so describing freezing deep to muscle, tendon, and bone is the best match. Mottled skin or nonblanching cyanosis can occur with frostbite in general but don’t specify how deep the injury goes, and a dry, black, mummified eschar can appear with necrosis but doesn’t alone define the deepest tissue involvement.