The eight-season run of House, M.D. has provided viewers with plenty of diagnoses to scratch their heads over.  Here are seven of the strangest:

Cushing's syndrome
A 10-year-old morbidly obese girl named Jessica complains of chest pains, and then suffers a heart attack at school in the first season of House, M.D.  While House's team originally suspects her obesity is to blame, Jessica's mother claims her daughter exercises daily and eats healthy.  When Jessica begins bleeding from necrosis on her chest, House's partner Dr. Chase realizes her obesity is a symptom â€" rather than the root â€" of her problem.  Jessica is diagnosed with Cushing's syndrome, or excessively high cortisol levels, which was caused by a tumor on her pituitary gland.

Chimerism
In the third season of House, the infamous doctor meets a 7-year-old who's been admitted to the hospital with rectal bleeding and hallucinations that he is being tortured by aliens.  Clancy, who was conceived through in-vitro fertilization, has conflicting results on multiple bleeding tests.  House and his team then realize the boy has cells with a different type of DNA in his body, leading House to diagnose Clancy with chimerism â€" a condition in which there are two sets of DNA in one body â€" due to Clancy's twin brother merging with him in the womb.  

Myoma
In season five, House and his team tackle the case of Dayna Miller, a woman who collapses in the middle of a cooking class.  While at the hospital, Miller's stomach fills with blood from her liver, and she develops an itch so bad she scratches through her own skull, causing brain matter to seep out.  A scan shows she has masses in her lungs, spin and pericardium, and then her heart stops, causing her to also bleed into her pericardium.  When House discovers Miller is also menstruating, he realizes that a past myoma surgery must have dispersed endometrial cells into her bloodstream, which then attached to different organs, multiplied and began bleeding during menstruation.  The team treats her by cutting out the masses of endometrium.

Von Hippelâ€"Lindau disease
An Air Force pilot who complains of ‘seeing' sounds visits Dr. House secretly to protect her dreams of becoming an astronaut for NASA.  When she suffers a heart attack, then later breathing problems, House suspects she has lung cancer and asks for a biopsy.  The doctors find cysts on her lungs indicative of Von Hippel-Lindau disease, a genetic condition that causes loss of vision.

Nephroptosis
When a woman collapses at her wedding, House struggles to find out why.  In the hospital, she stabilizes, but then crashes every time she tries to stand up again.  Just before surgery for internal bleeding, House asks her to stand, then presses a spot underneath her rib cage, which stabilizes her.  He diagnoses her with nephroptosis or ‘floating kidney,' which is the root of all her symptoms.

Pulmonary embolism (due to dental work)
In the season five finale, a bus that House was riding unexpectedly crashes.  House orders his team to check the bus driver for signs of a possible seizure.  After observing the driver for some time, the team speculates he could have Parkinson's disease, due to his shuffling feet.  However, when the driver suffers a pulmonary embolism and is intubated, House sees the driver had recent dental work done.  He deduces that an air bubble during the procedure was accidentally injected into the patient's blood stream through his gums.

Fat embolus
House must treat a patient through a webcam when a psychiatrist collapses and vomits in the middle of Antarctica.  The team considers kidney stones and a urinary tract infection as possible causes.  However, the patient's right lung then nearly collapses â€" though she shows no signs of cancer.  When her kidney shuts down and she later collapses into a coma, the doctors eventually realize she has a fat embolus, caused by a broken big toe.