A newborn girl, from an unremarkable term pregnancy and a spontaneous vaginal delivery without complications, had asymmetric crying when first observed in the nursery. Physical examination showed deviation of the labial commissure inferiorly to the right (Fig. 1 and Video S1), without other facial asymmetries, particularly eyelid closure or supraciliary contraction. At rest, there was no facial asymmetry (Fig. 2) and the remaining physical examination was normal.What is the diagnosis? (Answer on page 33