What condition is indicated by painful vesicles and punched out erosions in a patient with atopic dermatitis?

The presence of painful vesicles and punched out erosions in a patient with atopic dermatitis is indicative of eczema herpeticum. Eczema herpeticum occurs when the herpes simplex virus infects a skin area that has been compromised by atopic dermatitis. The vesicles typically appear on an already excoriated or inflamed skin and can cause significant pain and discomfort.

The "punched out" appearance of erosions seen in this condition stems from the viral infection, which leads to the destruction of the epidermal layer, creating superficial ulcerations that can be recognized clinically. The underlying atopic dermatitis predisposes the skin to viral infections such as herpes simplex due to the impaired skin barrier and increased inflammation.

Recognizing eczema herpeticum is crucial, as it requires antiviral treatment to manage the viral infection effectively, in contrast to other dermatitis or infectious conditions that might not present with this specific vesicular pattern and would require different treatments.