ankylosing spondylitis: a chronic form of spondylitis primarily in males and marked by impaired mobility of the spine; sometimes leads to ankylosis
autoimmune disease: any of a large group of diseases characterized by abnormal functioning of the immune system that causes your immune system to produce antibodies against your own tissues
keratoacanthoma: skin tumor that grows rapidly (especially in older people) and resembles a carcinoma but does not spread; it usually disappears spontaneously, often leaving a scar