Transient Pigmentary and Demarcation Lines in a Newborn: A Case Report.

Transient pigmentary lines of the newborn (TPLN) is a rare, benign condition characterized by spontaneously resolving hyperpigmented linear patches oriented along skin lines across the trunk and extremities. We report the case of a seven-week-old female who presented with innumerable hyperpigmented lines on the abdomen, dorsal feet, and ankles, as well as a sharp demarcation line separating different pigmentary segments of the upper and mid-chest from lower chest and abdomen. These findings all resolved by 1 year of age. This case expands our understanding of TPLN's variable presentations, possible etiology, and supports its classification as a self-limited, non-pathologic entity.