Police are seeking your help to find Gerald Penn, a 63-year-old Western Addition man who disappeared on Saturday afternoon.

According to the San Francisco Police Department, Penn, who suffers from "a severe case of Alzheimer's" disease, was last seen on December 27 at around 2 p.m., as he left his home on the 1000 block of Eddy Street, which is between Laguna and Gough Streets near Jefferson Square Park.

SF Weekly notes that Saturday was Penn's 63rd birthday.

SFPD spokesperson Officer Albie Esparza says that Penn's dementia is so severe that he "can say his name but cannot communicate much else." He is described by police as "unaware of his surroundings and cannot provide his address if asked."

Penn also has high blood pressure, for which he needs regular medication.

Police describe Penn as a black man with brown eyes and gray hair. He stands about 5 feet 8 inches tall, weighs around 140 pounds, and was last seen in a blue shirt, blue jeans and black shoes.

Have you seen Penn, or know anything about his disappearance? If so, please call 911 or (this isn't the usual number we give you here, so pay attention) call SFPD at 415-553-1071.