A low anterior hairline is a physical trait characterized by the downward extension of the scalp hair onto the forehead, resulting in a shortened distance between the hairline and the eyebrows. In clinical anatomy and dysmorphology, the hairline's position is defined by the trichion, which is the point where the forehead meets the hair-bearing scalp in the midline.
In the context of medical genetics, a low anterior hairline is frequently categorized as a minor physical anomaly. While it can occur as a normal variation in the general population—often influenced by familial and ethnic background—it is also associated with several congenital and genetic syndromes. It is a recognized feature in conditions such as Cornelia de Lange syndrome, Turner syndrome, Noonan syndrome, and certain types of mucopolysaccharidoses (such as Hurler syndrome).
The assessment of a low anterior hairline is primarily qualitative and relies on clinical observation during a physical examination. Although often evaluated subjectively, clinicians may use anthropometric measurements, comparing the forehead height (the distance from the glabella to the trichion) against standardized growth charts for specific age and sex populations to determine if the placement is statistically significantly lower than the mean. When present with other dysmorphic features, it may serve as a diagnostic indicator for underlying developmental or genetic disorders.