"Big Baby" is the thirteenth episode of the fifth season of House and the ninety-ninth episode overall. It aired on January 26, 2009.
Plot
Sarah, a 29-year-old special education teacher, coughs up blood and collapses. ITP and lymphoma are considered. House orders the team to start Sarah on methotrexate for the ITP and also wants to give her total body irradiation. Cameron has been hired by Cuddy as a temporary replacement. The methotrexate is not working. House therefore has his team double the dose and add prednisone, as well as fake the radiation treatment. While she is being "irradiated", she needs to urinate. When she gets up, she collapses. Thirteen and Taub discover that she has no pulse and defibrillate her. Meanwhile, Wilson visits Cuddy. Cuddy reveals that she is having trouble bonding with Rachel. Wilson tells her to just give it time. Also, Foreman is troubled by his discovery that Thirteen is on a placebo, and consults with Chase about surreptitiously switching her to the real thing. Chase tells him that this is unwise. Tests revealed no structural heart defects, and after some deliberations the possibility of cold agglutinin disease is raised. House wants to give the patient an ice bath to confirm, and goes to Cameron again. Cuddy stops by at the hospital. She has found out about Cameron's permissiveness with House and admonishes her. House barges in while the two are talking. He brings up Cuddy's bonding problem, and suggests giving Rachel up. Cuddy leaves, and Cameron tells House to perform a test on a sample of the blood before trying the cold bath. The blood clots when exposed to cold, but when the patient is put in the cold bath, her vital signs remain normal. While she is in the cold bath, Sarah recounts a story about how she became a special needs teacher. Six years ago, she transposed a room number and went to the wrong class. House decides that this is a sign of a left hippocampal lesion due to multiple sclerosis and wants a brain biopsy. Kutner suspects a pancreatic tumor and wants to perform an ERCP. Both go to Cameron, who orders him to scan the patient's brain first. The MRI is normal, but when Kutner performs the ERCP, Sarah begins to have trouble breathing – she has pleural effusions. House now suspects equine encephalitis and tries to get approval for a nerve conduction test. He goes to Cameron again, who stands up to House and denies the procedure. Thirteen and Foreman go to the school to look for any sign of equine encephalitis but find nothing. Thirteen expresses her interest in being a mother. Wilson again visits Cuddy's house, with a picture frame of what Rachel will roughly look like in 18 years. He tries to convince her that, right now, Rachel is only a baby who is not able to interact with Cuddy in the way she expected, but in time she will. After this, House goes to Cameron again, and pressures her into letting him run the nerve conduction study. A skeptical Kutner calls Cuddy and puts her on speakerphone in the middle of the procedure. Cuddy talks to House and the team. Sarah reveals that she is becoming annoyed by the crying, but her blood pressure falls significantly and the test is ended. The annoyance intrigues House, however, as it seems that Sarah is normally very tolerant of annoyance. While the procedure is ongoing, a desperate Cuddy pleads with Rachel to stop crying. Rachel stops crying, and Cuddy finally feels a bond. Also, Foreman, having asked everyone else he knows, goes to House about switching Thirteen's drugs. House tells him that rationally it is not worth it. Cuddy stops in his office with Rachel. She lets House hold Rachel, who throws up on House's shirt. Suddenly, House realizes what is wrong with Sarah: a patent ductus arteriosus. The ductus arteriosus allows blood to bypass the lungs while developing. When the infant is born, it normally closes, but Sarah's opens during periods of stress, draining deoxygenated blood into her aorta. This means that her brain does not get normal levels of oxygenated blood. It also disrupts normal pulmonary blood flow resulting in the pleural effusions and causes excessive turbulence in the bloodstream causing the damaged platelets. At Cuddy's house, Cameron decides to quit, saying that she will always say "yes" to House due to their relationship, and that any other person would always say "no" – Cuddy is the only one that can do the job. Finally, Foreman decides to risk his medical career for Thirteen's sake and switches her from the placebo to the real drug, while Cuddy is shown rushing to work again, leaving Rachel at home with a caregiver. As Cuddy walks toward the door, the baby suddenly starts crying again. Cuddy pauses a moment with the strain of separation showing in her face, but then continues without looking back.
