In third grade, Warhol had Sydenham's chorea (also known as St. Vitus' Dance), the nervous system disease that causes involuntary movements of the extremities, which is believed to be a complication of scarlet fever which causes skin pigmentation blotchiness. At times when he was confined to bed, he drew, listened to the radio and collected pictures of movie stars around his bed. Warhol later described this period as very important in the development of his personality, skill-set and preferences. When Warhol was 13, his father died in an accident.