Diane finds two small, red bumps on her foot; within hours her foot is swollen and appears black and blue; despite undergoing tests, the medical team has no diagnosis.

After blisters appear all over the body of young Julie McCawley, she appears to have Stevens-Johnson syndrome; Conor Heybach's weight gain and uncontrollable appetite is a mystery until a doctor discovers he has Prader-Willi syndrome.

Carole, a 65-year-old woman, has a hard time walking in a straight line; Sonya and Sherwood are delighted with their second daughter, but they begin to worry when the baby does not stop crying. When a particularly unusual symptom emerges, followed by uncontrollable seizures, it is discovered that the infant is affected by maple syrup urine disease.

Walt has always been in good health until one day he suddenly faints; when he arrives at hospital, his blood pressure is very low and he has gained 100 lb (45 kg) of weight in water. It is eventually discovered that he is suffering from systemic capillary leak syndrome.

A college student's body is covered in blisters and her colleagues fear it will be contagious; a nurse has paralyzing back spasms and may lose her job.

A woman feels uncontrollable pain in her menstrual period; a girl tries to lead a normal life, despite being covered by tumors.