<prompt> Answer this question truthfullyWhich population is commonly affected by mixed connective tissue disease, and what are the shared features of this condition with systemic lupus erythematosus, systemic sclerosis, and polymyositis?  <response>: <reason> Mixed connective tissue disease commonly affects adult women, and is characterized by shared features of systemic lupus erythematosus, systemic sclerosis, and polymyositis. 