Final answer:
Cystic acne is the most severe form of acne and is categorized as grade IV. It is characterized by pus-filled cysts resulting from bacterial infection of inflamed hair follicles.
Step-by-step explanation:
Cystic acne is considered the most severe grade of acne and it is typically referred to as grade IV. This form of acne is characterized by the presence of inflamed and pus-filled lesions, commonly known as cysts, within the skin. These cysts form due to bacterial infections of inflamed hair follicles, resulting in purulent or suppurative conditions, also known as furuncles. These large whiteheads, typically seen on the cheeks, indicate a high severity of acne.
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