Pseudoxanthoma elasticum (PXE) is an inherited disease with many systemic complications. Its diagnosis can be easily overlooked. The purpose of this study was to assess a new clinical sign of PXE. A total of 47 consecutive patients with PXE were examined for mental creases and compared with 47 age-matched control patients. Photographs were evaluated by a blinded investigator. Mental creases were present in 43 of 47 patients with PXE, affected the majority of individuals in every age group, and were significantly more common than in control patients (P <.0001). Under the age of 30 years, two thirds of patients with PXE had mental creases whereas mental creases were not present in any age-matched control patients. Mental creases commonly occur in patients with PXE. In young patients they are a sensitive and highly specific physical finding of this disorder. The presence of exaggerated mental creases is, thus, a useful physical marker for PXE.