Doctors are baffled by a woman's mysterious respiratory problem. Featuring Cushing's syndrome, gout, carcinoid cancer.

A child with celiac disease is intolerant of gluten; a woman has her left frontal lobe removed to stop seizures; another woman suffers from fatigue and mood swings. Featuring celiac disease, mitral valve prolapse (MVP), epilepsy.

A child with Hurler's disease undergoes a stem-cell transplant procedure; a woman is diagnosed with myasthenia gravis; A father has seizures and fainting spells due to a heart arrhythmia. Featuring Hurler syndrome, myasthenia gravis, cardiac arrhythmia.

A young boy's body is not producing antibodies to fight infections; a cancerous tumor must be removed; a woman loses the ability to walk. Featuring common variable immunodeficiency (CVID), gastrointestinal stromal tumor (GIST), reflex sympathetic dystrophy (RSD).

A 5-year-old has a persistent fever and stomachache. A man crippled with a neck tilt. A woman falls ill after traveling abroad. Featuring Crohn's disease, cervical dystonia, brucellosis.

Two brothers suffer the same heart problem. Joanne suffers from joint pain, mouth ulcers, genital sores, skin lesions, and vision problems. Featuring Barth Syndrome, Behcet's Disease

A baby is irritable, has trouble nursing and stops gaining weight. When the infant begins suffering repeated seizures and eventually begins sustaining rapid-onset cerebral ischemia, they are diagnosed with moyamoya disease, and must be treated before they suffer lethal brain damage from the repeated ischemic incidents. A man initially diagnosed with hypoglycemia finds out he's got a tumor in his lung. A woman battling coughs, hives, and muscle weakness, was revealed to have an elevated eosinophil count.

A baby drinks excessively, projectile vomits and stops growing. A professional baseball player's wife struggles to get pregnant due to a brain tumor. An old man is robbed of his eyesight.

Parents deal with a son with sinus infections and unsteady feet; a woman gains weight and has oily skin, hair loss, body cramps and irritable bowel syndrome. A reverend has trouble sleeping.

A man has suffered from vertigo and ear infections since childhood. A 16-year-old girl has headaches and neck twitching, that led to preeclampsia. A girl has a serious heart condition and stops growing and gaining weight.

A baby's hair appears brittle, and she is slow in developing after a case of whooping cough. Following a tube-tie procedure, Jackie contracted a flesh-eating disease. A boy develops nosebleeds, a sign of something much more terrifying.

A baby shows signs of a genetic disorder. A college graduate developed bloating, decreased sex drive, and yellowing of the eyes. Since childhood, Scott has battled an array of symptoms—severe joint pain, strange rashes, and an inability to sweat. Could his symptoms be related to his kidneys?

Roman was a baby when his parents noticed his head always tilting to one side and his eyes rolling back into his head when he looked up. Could the cause be just one condition? Sharon was an active varsity diver but after a car accident, she developed an unquenchable thirst that would soon take over her life. Peggy lived a healthy and active lifestyle, until one day when the mother of two experienced coughing, joint pain, and swelling.

Nicky was a healthy five-year-old boy until terrifying symptoms landed him in the hospital, fighting for his life. Kristine was a super mom until crippling abdominal pains would change her life forever. Jackie was active until mysterious pains wracked her entire body, eventually becoming so bad that she had to drop out of school.

A baby boy suffers from the same symptoms that killed off male offspring on his mother's side of the family, Could doctors figure out what it is before it's too late? A man in his late thirties experiences a constant, painful burning sensation in his chest, making breathing difficult, but an initial trip to the ER reveals nothing. A woman lives with joint pain, redness in her eyes, and a blood test revealed an elevated anti-nuclear antibody.

A girl sleeps for ten days in a row, but tests are normal and doctors are perplexed; a marathon runner experiences unexplainable fatigue.

A doctor makes an unexpected discovery when he operates on a young woman; doctors try to reach a diagnosis when a marathon runner experiences mysterious fatigue.

A man suffers from a series of debilitating symptoms; doctors cannot diagnose his illness, but thanks to a chance meeting this mystery will be solved; a woman undergoes a risky left temporal craniotomy.

A teenager is rushed to the hospital after taking aspirin to help alleviate altitude sickness; a woman has pain in her arm that mysteriously spreads.

A woman and her husband decide to start a family after numerous negative pregnancy tests; a man appears to suffer an embolism

A 3-month-old boy has breathing difficulties; a woman has stomach problems; stepping on a crochet hook causes strange problems for a patient.

An infant shows diverse symptoms; an ER nurse gets a diagnosis of lymphoma, before another symptom reveals her true illness.

Brenda and Jake are delighted when their daughter Isabel is born, but their euphoria quickly turns to panic when Isabel stops eating and her skin turns grey. Noah and Alexis were healthy twins until they suddenly lost all their milestones. Charlie, an active pastor, has difficulty reading; doctors must act quickly to save his eyesight.

Doctors wonder why an apparently healthy baby fails to achieve its developmental goals; on the other hand, a woman who seemed to be in good health suddenly becomes ill.

A woman experiences chronic stomach pain and diarrhea attributed to irritable bowel syndrome; another faces extreme fatigue and night sweating while pregnant.