Also known as: Sexually transmitted infection
George discovers he has contracted syphilis, likely from Olivia, leading to a hospital-wide outbreak affecting multiple staff members. This drives a major subplot involving his relationship, embarrassment, and a mandatory safe-sex education session.
Also known as: Chimera with ovarian tissue
Bill presents with abdominal pain and blood in urine. Cystoscopy reveals a mass that turns out to be an ovary due to gonadal hermaphroditism from chimerism (two embryos merged). During surgery, doctors discover he has a blind vas deferens, meaning he is sterile and cannot be the father of his wife's expected baby.
Also known as: Iron overload
Mr. Franklin presents with massive ascites, presumed to be from alcoholic liver disease. During paracentesis, he dies unexpectedly. Cristina and Izzie perform an unauthorized autopsy and discover he had hemochromatosis causing iron buildup in his heart (over 600 grams), which led to heart failure. The genetic discovery prompts testing of his daughter Alice.
Also known as: Abdominal fluid buildup
Mr. Franklin's presenting symptom is massive abdominal swelling from fluid accumulation, initially attributed to liver disease from alcoholism. Interns perform paracentesis to drain the fluid.
Also known as: Brain tumor affecting vision
Chief Webber experiences blurry vision during surgery and seeks Derek's help confidentially. MRI reveals a tumor pressing on his optic nerve. Derek operates in a secret surgery, with risk of permanent blindness as a complication.
Also known as: Early-onset Alzheimer's
Meredith's mother Ellis has advanced Alzheimer's and lives in a nursing home. Meredith has been keeping this secret from everyone. The episode reveals Ellis had a lucid moment asking for her daughter, causing Meredith emotional distress about her relationship with Derek.