Problem: A patient seeing a rheumatologist for the first time is asked to fill out forms that include questions about family history. She recalls many family members with "arthritis," including her grandmother and great-aunt. Her mother has systemic lupus erythematosus (SLE) with arthritis symptoms and renal disease. Her mother's siblings are healthy, as are the patient's father and younger sister. This family history is most suggestive of which of the following? a. a microbial infection common to all afflicted family members. b. X-linked Mendelian genetics. c. bad luck. d. a genetic predisposition.