What chronic skin disease involves erythematous papules that coalesce to form plaques with distinct borders?

The condition described involves erythematous papules that can combine to create plaques with distinct borders, which is characteristic of psoriasis. Psoriasis is an autoimmune disorder that leads to rapid skin cell production, resulting in thickened areas of skin that can appear red and scaly. These plaques typically have a well-defined edge, differentiating them from other skin conditions.

Unlike eczema or dermatitis, which often manifest with irritation and inflammation in a less defined manner, psoriasis features more distinct and raised borders around its plaques. While acne is primarily associated with comedones and inflammatory lesions, it does not exhibit the plaque-like formation seen in psoriasis. Therefore, the unique presentation of well-defined plaques of erythematous papules makes psoriasis the correct answer to this question.