<prompt> Answer this question truthfullyWhich form of Raynauds phenomenon is characterized by asymmetric attacks with clinical features of tissue ischemia, such as numbness and ulcers, primary or secondary?  <response>: <reason> The form of Raynauds phenomenon that is characterized by asymmetric attacks with clinical features of tissue ischemia, such as numbness and ulcers, is secondary Raynauds phenomenon. Secondary Raynauds phenomenon, also known as Raynauds syndrome, is a condition in which the blood vessels in the fingers and toes constrict excessively in response to cold temperatures or emotional stress, similar to primary Raynauds phenomenon. However, unlike primary Raynauds phenomenon, secondary Raynauds phenomenon is typically associated with an underlying medical condition such as lupus, scleroderma, or rheumatoid arthritis, and can cause tissue damage due to reduced blood flow. The attacks in secondary Raynauds phenomenon are often more severe and prolonged than those seen in primary Raynauds phenomenon, and may require medical treatment to prevent complications such as ulcers or gangrene. 