Arc Words: Mystery Diagnosis is very fond of these. They include:
For some unknown reason
In healthy individuals [explanation of how a healthy body works.] But in patients like [patient name], [explanation of disease's effects.]
"Nothing short of shocking" is used to describe test results often.
"Nothing could have prepared [X] for what [Y] revealed/what happened next/what they saw", etc.
New symptoms are always described as "emerging" or "stopping [X] dead in their tracks." New symptoms are also often characterized as "frightening," "even more frightening," or "bizarre."
Towards the end of the segment, expect a variation of "But why did it take so long for the doctors to diagnose the condition?". This is almost always worded as He/She/They "can't help but wonder" why the condition took so long to diagnose.
Each episode also has variations of comparisons between patients, because some of them have symptoms too debilitating to ignore, while others' symptoms act like a sleeping giant, and still others have symptoms, but don't do anything about them for a long time.
"Head-to-toe exam" and "thorough head-to-toe exam" are also used a lot.
There will often be a reference to "If you hear hoofbeats, look for horses, not zebras," and an admission that this condition was in fact a zebra.
Adult Fear: The reason the show is rated TV-14. This is especially true of the parents you see on the show with babies or young children. Actually, the whole thing can be rather freaky (see below).
Babies Make Everything Better: Maria Lazazarro, the mother in "The Girl Who Stopped Growing," invokes this trope. She explains that her daughter's being born with mysterious disabilities took a toll on her marriage and that when she and her husband decided to have a second baby, they figured it would fix things. The baby, little Samantha's brother Jake, was born with the same disabilities, later diagnosed as Cockayne Syndrome. The couple divorced after Jake was born.
Big Eater: The patient in the second half of "The Boy Who Couldn't Stop Eating," Connor Heybach, has Prader-Willi Syndrome. It's a condition in which the hypothalamus malfunctions, keeping the person with it from ever feeling full no matter how much or often they eat.
Also occurred with little Haven Fowler in "Trapped Inside their Bodies." One of the main symptoms of her ROHAAD Syndrome is rapid weight gain/obesity and eating great quantities of food in your sleep.
Completely inverted with Samantha Mina, who suffers from SMA Syndrome. This affects one of the arteries in the intestine and makes it impossible to eat without vomiting, cramps, and extreme pain.
In addition, commonly inverted with anyone whose symptoms include significant stomach issues, which often leads to weight loss and total or almost total loss of desire to eat.
Body Horror: To varying degrees depending on the episode you're watching. In some, the worst you'll get is a close-up of a blood draw. In others, you'll see close-ups of horrific rashes, bruising, or in one case, a home video of a boy whose psychological symptoms made him act in "bizarre" ways, such as exhibiting motor and verbal tics at an alarming rate. In the episode focussing on MSU Disease, surveillance footage is shown of the child afflicted with the condition convulsing violently on a hospital bed.
Critical Research Failure: Both literally on behalf of incorrect diagnoses, and figuratively in the case of one of the show's catchphrases ("But why did it take so long for the doctors to diagnose the condition?") - Never have any of the diseases featured not been known to science and medicine, but they often masquerade as other conditions, such as the improper deployment of Anti-Yo Antibody damaging the cerebellum, causing Paraneoplastic Cerebellar Degeneration being mistaken for dementia.
Doctor Jerk: Some of the doctors on the show act like this, especially the ones who are treating children (notably girls) and tell the parents the kid is just being overly dramatic, when the parent knows something is really wrong or the child is clearly in pain or distress.
Edutainment Show: Of course, nothing is a substitute for actual medical advice, but if you're a big fan, you will learn a lot about rare diseases and symptoms.
Gross-Up Close-Up: Sometimes, particularly if the patient of the day is suffering from a flesh-eating disease (which happened a few times). This can also happen with large amounts of blood, or even diagrams (such as those that show cholesterol building up around a heart).
I Just Want to Be Normal: Lampshaded and played straight. Naturally, contributors' illnesses make them feel this way, and they say it. Many parents fear that mysterious conditions will keep their kids from being "normal" children as well.
Incurable Cough of Death: If an episode involves a respiratory condition, expect plenty of coughing, which can be mistaken for this. Justified in that sometimes, the respiratory symptoms do all but kill the featured patient.
Mama Bear: Some of the moms of young children on the show who, when confronted with doctors who basically tell them to go home and quit stressing over their kids, tell the doctors to shove it and start doing their own research.
Once an Episode: Often multiple times an episode, usually before commercials, the camera will do a close-up of someone's eyes, usually the eyes of the person the featured disease tried to ravage.
One Steve Limit: Averted; several featured patients have the same first names. The series has hosted:
At least two Amandas (Koveler and Nixon)
Two Ashleys (Wolf and Mulinax)
Two Connors (Heybach and Rowley)
Two Katies (Wells and Faust)
In a last name example, a Len Geiger and a Jake Geiger.
Papa Wolf: The counterparts to the Mama Bears, though this happens less than with moms.
Screwed by the Network: Lord, YES, at least in the U.S. Episodes are in different time slots, in different orders, at least once every month. They can be shown in marathon blocks, once a week, not for months at a time...screwed royally.
Stock Footage: The series uses some to show the changes of the seasons, such as a red autumn tree and snow flurries in a pine forest. Some episodes also use Stock Footage of hospital hallways.
Trademark Favorite Food: A variant; it's more of a Symptomatic Favorite Food. Applies to any illness that makes the patient crave certain foods to get the nutrients or ingredients in them. Salt is a common craving-inducer, which usually indicates a kidney problem. Some patients also experience intense cravings for water.
Two First Names: Patient Kylie Monica and Dr. Carrie Judy (from two separate episodes).
Woobie of the Week: The patients understandably become so distraught over their illnesses, they pretty much have to be this. Especially true in the case of kids.
Your Princess Is in Another Castle: Happened a couple of times, where the actual diagnosis was not a diagnosis itself, but a hallmark of some other disease. Examples included cold agglutinin disease as a hallmark for undiagnosed leukemia and Crohn's symptoms as a cover for a disease called Hermansky-Pudlak syndrome.
Sometimes happens because the guests are diagnosed with some type of common or mild disease. They are given medication that seems to work for awhile or clears up the symptoms completely, but then stops working or doesn't respond to a new symptom. Can also happen in cases where the treatment or side effects related to the real diagnosis are actually more devastating than the disease itself.