E.T. is a 42-year-old female who has been all tired out for the past few months. The onset of her illness was poorly defined, and aside from a lack of energy she has no other complaints. She reported being easily winded or short of breath when climbing the stairs or walking for any prolonged distance. She told her doctor that she had recently experienced a slight weight loss following the loss of her mother. What diseases or conditions should be considered in this patient? What additional information do you need to make a correct diagnosis?