5 of the World's Most Ultra-Rare Diseases


There are few times when your doctor or physician will utter the phrase, "I don't know" to a patient, but when you're dealing with the rarest of diseases, then all bets are off.

According to the Food and Drug Administration, a rare disease or disorder is any one that affects 200,000 of fewer people. That's actually a pretty broad range that can encompass potentially thousands of diseases. Today, I want to focus on the rarest diseases of them all -- the ultra rare of ultra-rare diseases, if you will!

DNA sequence found in Science Museum, London. Source: John Goode, Flickr.

Unfortunately, because record keeping and studies of certain disorders are still ongoing (and diseases are still being identified) there is no master list of the world's rarest diseases. That's why today I'm outlining five of the rarest (not necessarily the top five) diseases that affect people around the world that I've come across in my research. But, before I begin I'm going to state that I've excluded both polio and smallpox from the discussion. It's true that they are among the rarest diseases in the world today, and you'll often find them atop rare disease lists, but that's only because vaccinations were developed following the deaths of millions of people. Instead, I want to focus only on unsolved ultra-rare diseases.

5. Hutchinson-Gilford Progeria
More often referred to as Progeria, this disease affects about one in every 8 million children and, due to a genetic mutation, causes the appearance of rapid aging beginning in early childhood. Symptoms often include baldness, a large head relative to their body size, limited range of motion, and most tragically, a hardening of the arteries in many cases -- which increases the chance of heart attack or stroke. In medical history, only about 100 cases of Progeria have been documented with few patients living into their 20s.

4. Methemoglobinemia
Known more commonly as blue skin disorder, this disease is characterized by an abnormal amount of methemoglobin, a type of hemoglobin that's transformed to carrying iron, in a person's blood. Most of us have less than 1% methemoglobin in our blood stream, whereas those who suffer from blue skin disorder possess between 10% and 20% methemoglobin. Because iron-carrying hemoglobin carries only a reduced amount of oxygen, patients diagnosed with methemoglobinemia are at higher risk of developing heart abnormalities, having a seizure, or even dying prematurely. The disease has been made most famous by a single family in Kentucky who appear to have passed the genetic trait onto its family members for some 200 years.

3. Kuru
There's a really, really good chance you're not going to contract Kuru as it's a disease that can only be found in a remote region of New Guinea in the Fore tribe, according to Discovery Health. The disease itself is caused by a type of protein called prions, which induce abnormal brain tissue building resulting in progressive and incurable brain damage. The disease itself is 100% lethal, but it's only possible to acquire it these days by -- wait for it -- eating the brains of an infected victim. Prior to the 1950s, the Fore tribes' rituals involved consuming their dead in order to preserve their spirit, which often led to transmission of the disease. With cannibalism outlawed, the disease is practically nonexistent today.

2. Fields Condition
We're definitely getting into the nitty-gritty of the world's rarest diseases when we're talking about Fields Condition, a progressive muscle disorder that affects two sisters (Kirstie & Catherine Fields) and can cause painful muscle spasms up to 100 times each day. The disease is still predominantly a mystery to doctors, but in its wake it's paralyzed both sisters and cut off their ability to speak, with the two now relying on electronic speech machines to communicate.

1. RPI deficiency

According to the Journal of Molecular Medicine, Ribose-5 phosphate isomerase deficiency, or RPI Deficinecy, is the rarest disease in the world with MRI and DNA analysis providing only one case in history. In 1984, the patient in question presented with a white matter disease as found on an MRI and was finally diagnosed in 1999. The molecular cause of the genetic pathway malfunction is still to this day not understood.

Source: U.S. Fish and Wildlife Service Northeast Region, Flickr.

Five companies on your side
There's no question that it'd be great if we could develop treatments to help those suffering from even the rarest of diseases, but five biotech companies have geared all of their effort and their pipeline toward ultra-rare diseases. Here they are in no particular order:

  • Alexion Pharmaceuticals : Perhaps the poster child for ultra-rare diseases, Alexion has found incredible success with its only FDA-approved drug, Soliris, to treat paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Since both diseases are classified as ultra rare, Alexion has had no trouble in dealing with competitors and in getting insurance companies to cover its $400,000-plus per year drug. Many ultra-rare drug companies have a hard time recouping their development costs of a drug; but not Alexion with Soliris.

  • BioMarin Pharmaceuticals : BioMarin currently has four drugs commercialized for ultra-rare diseases including Naglazyme for mucopolysaccharidosis VI, Aldurazyme for mucopolysaccharidosis I, Kuvan for the treatment of PKU, and Firdapse, which is currently approved in the EU for the treatment of Lambert-Eaton Myasthenic Syndrome. Like Alexion, there is little competition on the horizon for BioMarin, which means that many of its approved drugs are among the most expensive in the world. Profits are continuing to elude BioMarin thus far because of its heavy R&D investments, but it's certainly developing quite the niche in ultra-rare diseases.

  • Aegerion Pharmaceuticals : Aegerion's early claim to fame is its pill to treat homozygous familial hypercholesterolemia, or HoFH, known as Juxtapid. Priced at $295,000 per treatment, it's significantly pricier than Kynamro, a competing drug developed by Isis Pharmaceuticals and Sanofi, but it also offers some advantages. Ease of use, for one, since it's a pill versus Kynamro -- which is given intravenously -- and also from a safety perspective since Kynamro was associated with abnormal neoplasm growth in clinical trials. Aegerion is certainly having no issues marketing its HoFH drug to physicians as it basically doubled its sales projections for the remainder of 2013.

  • NPS Pharmaceuticals : Also priced at $295,000 per year is NPS' recently approved short bowel syndrome drug, Gattex. As my Foolish colleague Keith Speights points out, NPS' estimates its target audience at between 3,000 and 5,000 adults annually, which could add up to more than $1 billion in sales when all is said and done. Like Aegerion, NPS does have some competition in this space, but sales potential is rapidly growing. According to its first-quarter report, 42 patients were on its SBS drug with NPS commenting in June that 200 to 300 patients should be taking Gattex by year's end.

  • ViroPharma : Often the forgotten stock of the biotech group, ViroPharma's ultra-rare treatment extraordinaire is Cinryze, which it acquired when it purchased Lev Pharmaceuticals in 2008. Cinryze helps to treat hereditary angioedema, a disease that affects about 6,000 people in the U.S., and is among the most expensive drugs in the world. Like Soliris or Juxtapid, its high price hasn't slowed sales with Cinryze sales jumping 44% in the most recent quarter.

A true rarity can be a good thing
The interest we're witnessing from ultra-rare drug developers is certainly a positive sign. The success of Alexion and a few other players in the field has given more than enough encouragement to other biotechnology companies and even larger pharmaceutical players like Sanofi to enter the fray. There are literally thousands of orphan diseases yet to be untapped, so the opportunity for orphan and ultra-orphan drug developers is there for what I see as decades to come.

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The article 5 of the World's Most Ultra-Rare Diseases originally appeared on Fool.com.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.The Motley Fool recommends BioMarin Pharmaceutical. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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