- [Voiceover] Thousands of ailments plague the human race,
whether infectious or genetic.
Medical breakthroughs allow us to better understand,
control, and fight these diseases every day,
but all diseases are not created equal.
Some are so rare that research is limited,
either because of lack of funds or lack of patients.
Here are the top 10 most interesting rare diseases.
Smallpox is one of the great killers of history,
ravaging populations since before the advent of writing.
20% to 60% of all smallpox patients died,
and survivors are usually left
severely scarred by the ordeal.
By the mid-20th century, millions of people
were dying every year from the disease.
The first vaccination in the world was made to combat
smallpox, and over the course of less than two centuries,
this worldwide scourge was hunted to extinction.
According to the World Health Organization,
smallpox was eradicated from the human population by 1979.
People are no longer vaccinated for it.
The only remaining samples are in highly secured
American and Russian medical laboratories.
Smallpox is rare because it was exterminated.
Fields Syndrome is rare because literally no one gets it,
save the twins Katherine and Kirstie Fields.
First showing symptoms when they were four,
the twins have been put through rigorous testing,
but nothing has indicated that they suffer
from any known condition.
Fields Syndrome is a degenerative muscular disease
causing increasing difficulty with deliberate movement.
Currently, the twins use wheelchairs
and require electronic aids to speak.
There is no indication it affects the brain,
as rationality and personality remains intact.
Fibrodysplasia ossificans progressiva,
or FOP, is a genetic condition affecting
only one in two million people.
It causes bone to replace muscles, tendons, and ligaments.
This is exacerbated by injury, which means surgically
removing extraneous bone merely encourages the growth
of more, such as which operates the digestive track
and cardiac muscle are immune from this process.
FOP patients become trapped in their own bodies
as joints freeze into place.
Eventually the eating and drinking is compromised.
Growths over the ribcage limit breathing.
Life expectancy is less than 40 years.
Mad Cow Disease is the most well known
form of spongiform encephalopathy.
Its human counterpart, Creutzfeldt-Jakob disease,
or CJD, is another form.
Both are extremely rare diseases.
CJD only affects one in a million people.
But Kuru, confined to a single tribe
in Papua New Guinea is an even rarer form.
Patients lose muscle coordination until they are unable
to walk, and they suffer significant tremors.
Eventually they are unable to speak, sit up,
remain continent, or react to their surroundings.
Spongiform encephalopathy is most easily transmitted
through the eating of brain matter,
and the Papua New Guinea tribe perpetuated the disease
through ritual cannibalism, eating the dead returned
the disease strength back to the family.
These rituals were most often performed by women,
and women were almost 10 times more likely to develop Kuru.
Both missionaries and the government worked
to eliminate the cannibalistic practices,
and the disease may be extinct.
With decades of potential incubation, however,
a very few infected souls may still be alive.
Only one in eight million people are born
with Hutchinson-Gifford Progeria,
often known simply as Progeria,
literally meaning premature old age.
Patients appear to grow old
over the span of a very few years.
Symptoms start in infancy, including hardening of the skin,
loss of hair throughout the body, and an overly small face.
Later symptoms include blindness, wrinkled skin,
arterial sclerosis, heart issues, large head,
fragile bones, stiff joints, and loss of fat and muscle.
Conjoined twins are already rare,
with many dying soon after birth.
Parapagus Dicephalic twins are a tiny subsection
of that group, and only a handful are alive today.
Dicephalic twins have only one torso,
two legs, and somewhere between two and four arms.
Those with only two arms have the appearance
of being a two-headed person.
One such set of twins is Abby and Brittany Hensel,
currently 26 years old.
Each controls one arm and one leg.
Together, they can walk, run, drive a car,
swim, and most other everyday activities.
They have different opinions, interests,
and even favorite and least favorite foods.
Conjoined twins don't always survive in the womb.
Sometimes one dies and is absorbed by the other.
A possible result of this process is polymelia,
the having of extra arms or limbs.
Polymelia can have additional causes as well,
and cases of babies being born with as many
as six legs have been documented.
About one in 300,000 children are born
with Harlequin-type Ichthyosis,
which causes the skin to be covered
in small hard plates divided by deep cracks.
Ears, eyes, nose, and lips are often
deformed by the condition as well.
The cracks can capture bacteria,
so vigilant hygiene is a necessity.
The radical changes to their skin leave them
unable to efficiently regulate temperature
or retain moisture, so heat stroke
and dehydration are significant concerns.
Most patients die within days,
but some have survived into adulthood.
Ectopia Cordis is a condition in which the heart
is located partially or entirely outside of the torso.
Covered by only a translucent membrane, the heart lacks
the usual protection of bone muscle and tissue.
The heart often, but not always, is also deformed,
and most patients do not survive long after birth.
Surgery has met with some success,
but mortality rates remain high.
Epidermolysis Bullosa patients are known
as butterfly children because of the fragility
of their skin, which is likened to the wings of a butterfly.
Human skin is composed of two layers,
the dermis and epidermis.
In between the two are proteins
anchoring the layers together.
For patients with EB, those proteins are missing.
When you're afflicted by this disease,
your skin can easily be damaged,
resulting in blisters and lesions.
The danger comes when those injuries become infected
or when they are internal, such as inside the throat.
Many EB cases are mild.
However, patients suffering
the rarest form rarely survive infancy.
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And don't forget to check out our other lists.
And thanks for watching, and thanks for learning.
(ambient music)