Factual error: When Andie is going in for her MRI, Chase starts the machine with Andie's steel IV pole in the room. No doctor would ever do that considering the damage that would be done to machine and patient. (00:05:45)
Factual error: The patient is diagnosed with legionnaire's disease, caught from the AC unit above their desk. The legionella bacteria causing the disease is found in warm water (commonly dehumidifiers, industrial AC cooling towers, hot water tanks) - the key point being that a water source is required. The problem with this is that the AC unit above the patient's desk is a window unit. These sorts of AC units don't use water as a coolant - you can't catch legionnaire's from them.
Factual error: Cameron forces House (against his wishes) to do the biopsy on Foreman because Foreman has made her his medical proxy. This is completely incorrect; Cameron may be Foreman's proxy, but that doesn't mean she can overrule the attending doctor. Having the right of medical proxy allows her to *refuse* a test in Foreman's name (or refuse consent to any number of medical activities on Foreman), but absolutely not to order a test or operation contrary to the attending doctor's views. (00:34:45)
Factual error: Naegleriasis is a rare disease, and all the known cases involved people who had submerged their nostrils in contaminated water (commonly while swimming or diving). Foreman's exposure was just that he walked past a mister spraying contaminated water: nowhere near enough exposure to get infected. It's also highly unlikely Foreman would have survived Naegleriasis (which has an extremely high death rate) and without lasting brain damage - particularly given the length of time before diagnosis.
Suggested correction: They don't use water as a coolant, but they can collect water that condensed from the cold inside the unit.
LorgSkyegon
Which still doesn't allow for legionella to breed, not least the limited amount of collected water drains away (i.e. not like in water tanks and cooling towers). Healthcare professionals have consistently confirmed that window AC units aren't legionella risks for this reason. If you check the CDC website, it explicitly states that window AC units aren't potential legionella sources.