What condition involves sweat duct blockage in newborns?

Milia are small, white cysts that can occur on the skin of newborns, commonly seen on the face, particularly on the cheeks, nose, and forehead. These cysts form when sweat ducts get blocked, trapping keratin beneath the skin's surface. Since milia are often present in newborns, they correlate directly with the blockage of sweat ducts, making them the correct answer for the condition involving this specific mechanism.

In contrast, conditions like cutis marmorata, erythema toxicum, and vasculitis have different etiologies. Cutis marmorata refers to a lacy, mottled appearance of the skin due to temperature changes and is not due to sweat duct blockage. Erythema toxicum is a benign rash that's typically observed in newborns; it consists of red spots and is not linked to sweat duct obstruction. Vasculitis involves inflammation of blood vessels, which is unrelated to the function and blockage of sweat ducts.

Understanding the pathophysiology behind each of these conditions highlights why milia is specifically associated with the blockage of sweat ducts in newborns.