What clinical feature differentiates papules from patches?

The distinguishing clinical feature between papules and patches is indeed related to their size. Patches are defined as larger lesions that typically exceed 1 cm in diameter. This size criterion helps differentiate them from papules, which are smaller, raised areas of skin that generally measure less than 1 cm.

The statement about patches being flat is relevant but does not serve solely to distinguish them from papules, as flatness can be a characteristic of both. While papules can certainly vary in size, they are specifically categorized as being less than 1 cm. Additionally, it is not accurate to say that papules are always red and inflamed; they can vary in color and presentation, depending on the underlying cause.

Thus, the size specification of patches being larger than 1 cm is a clear and definitive characteristic that sets them apart from papules.