Which of the following is NOT a characteristic facial feature of FAS?

The characteristic facial features of Fetal Alcohol Syndrome (FAS) include a smooth philtrum, thin vermilion border, and short palpebral fissures. These features arise from the teratogenic effects of alcohol on facial development during critical periods of gestation.

A smooth philtrum is indicative of FAS because normal facial development includes a defined philtrum, which is often flattened or smooth in individuals with FAS. A thin vermilion border refers to the lip's delineation, which is typically well-defined in unaffected individuals; in those with FAS, the border is usually thinner and less pronounced.

Short palpebral fissures are another hallmark feature of FAS. This term refers to the horizontal openings between the eyelids, and in FAS, these fissures appear shorter than normal.

In contrast, long palpebral fissures are not characteristic of FAS. Instead, this feature would suggest a different condition. Thus, identifying long palpebral fissures as not being a characteristic of FAS aligns with the known manifestations of the syndrome, confirming why it is correct to state that it does not belong among the typical facial features associated with FAS.