The World's Rarest Diseases

Imagine having a disease so rare that it only affects one other person on earth—your sister. Kirstie and Catherine Fields, 18-year-old identical twins from Wales, are the only known sufferers of Fields Condition, a progressive muscle disorder that’s been named after them. It’s believed to be the world’s rarest disease.

Their disorder, which triggers more than 100 excruciating, uncontrollable muscle spasm a day, left the twins paralyzed and unable to talk until they received electronic speech machines for their birthday. There’s a “strong possibility” that their mysterious disease may cut their lives short, according to Wales Online.

Kirstie and Catherine have been using wheelchairs since they were 11 and lost their voices at 14. Yet the teens, who sport matching butterfly tattoos, have a surprisingly upbeat attitude and use their communication devices to tell jokes and enjoy girl talk.

Although there’s no cure in sight for the teens’ painful condition, on a recent TV documentary about their life, they told viewers, “Don’t feel sorry for us…No one lives forever. Be happy and smile.”

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February 28 marks Rare Disease Day, dedicated to raising awareness of the nearly 8,000 known rare diseases that collectively affect more than 60 million people around the world. Because these conditions often stem from genetic problems, 75 percent of those battling them are kids, reports

For most of these diseases, there’s no cure and many lack effective treatments. Yet rare disorders are often chronic, progressive, disabling, or even life threatening. Tragically, 30 percent of patients afflicted with these conditions die before age five.

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Here’s a look at some of the world’s rarest diseases:

  • Fibrodysplasia Ossificans Progressiva (FOP). Sometimes called “stone man” syndrome, this extremely rare genetic disease causes soft tissue to turn into bone, as if the person was slowly being petrified. As a result, movement in the affected areas becomes difficult or even impossible. The disorder is marked by painful flare-ups as the disease progresses along the trunk and then the limbs. There are only about 700 known cases around the world. There is no known cure for FOP, as surgery to remove the bony growths often results in even more bone formation, according to UCSF Benioff Children’s Hospital. However, a drug that may help control bone growth is being developed.
  • Hutchinson-Gilford Progeria. Usually called progeria, this fatal disease causes extremely rapid aging, starting in early childhood. As a result, kids with this condition develop wrinkles, baldness, and the shrunken face that usually occurs in the very elderly. Other symptoms include a large head and small body; thin, scaly skin; limited range of motion; and a soft spot in the skull. The disease also causes hardening of the arteries, causing up to 90 percent of sufferers to have heart attacks or strokes. Progeria only affects about one in 8 million people and most patients only live to about age 13, though some have survived into their early 20s.
  • Xeroderma pigmentosum (XP). Kids with this extremely rare genetic disease are sometimes called “children of the night,” because their bodies can’t repair damage from exposure to even tiny amounts of UV light, such as that from the sun. Up to half of sufferers develop skin cancer by age 10 and the leading causes of death for those with condition are melanoma and squamous cell skin cancer. Because the eyes are also painfully sensitive to sunlight, there’s also an increased risk for both eye cancer and vision loss, according to the National Institutes of Health. XP affects about one in 250,000 people and is triggered by a recessive gene, which must be inherited from both parents for the condition to occur.
  • Fatal familial insomnia. The nightmare of this disease is never to have a nightmare or even a dream. For centuries, members of an Italian family have been dying from a mysterious disorder in which they are unable to sleep. It was eventually traced to a genetic mutation that caused abnormal proteins in the brain, NBC News reports. To date, the disorder has only been found in about 40 families worldwide.
  • Blue skin disorder. For nearly 200 years, members of the Fugate family in Kentucky have been afflicted with an inherited disorder that gives their skin a startling blue or even purple hue. Medically known as methemoglobinemia, the condition results from a blood disorder that leads to an abnormal amount of methemoglobin—a form of hemoglobin. Sufferers have purple lips, blue skin, and chocolate-colored blood due to insufficient levels of oxygen, ABC News reports. High levels of methemoglobin can spark seizures, heart disorders, or even death.
  • Hereditary angioedema (HAE). For more than 20 years, Tanya Howell of Scottsdale suffered from mysterious, unexplained swelling attacks that left her in pain, debilitated, and unable to do the things she loved most in life. She consulted many specialists before being diagnosed with HAE, a rare disease marked by debilitating and potentially life threatening swelling that can occur anywhere on the body. It affects about one in 50,000 people worldwide. Bouts of swelling often make daily activities difficult or impossible, while attacks of the face can leave the patient deformed beyond recognition. The FDA has now approved four treatments for HAE, including Cinryze, a drug that combats swelling. Now that her symptoms are finally under control with medication, Tanyawho loves outdoor sportssays, “I can participate in life now.” 

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