The FDA describes rare diseases as a disease that affects less than 200,000 people. That’s actually a pretty big number and can include a huge number of diseases. Today, we are going to focus on some of the ultra-rare diseases.

 Hutchinson-Gilford Progeria

Medical professionals also call this disease Progeria. This disease affects about one in every eight million children. It is due to a genetic mutation that causes the appearance of rapid aging beginning in very early childhood. Symptoms often include baldness, a large or oversized head in relation to their body size, limited range of motion, and in most cases, a hardening of the arteries which greatly increases the likeliness of stroke or heart attack. In medical history, only about one hundred of the cases have lived into their early twenties. Most children die around the age of 13.


This disease is most commonly known as blue skin disorder. It is characterized by an abnormal amount of methemoglobin, a type of hemoglobin that’s transformed to carrying iron through a person’s blood. Most of us have less than one percent of methemoglobin in our blood stream, but those who suffer from blue skin disease possess between ten percent and twenty percent of methemoglobin. Iron- carrying hemoglobin carries a highly reduced amount of oxygen, so patients diagnosed with Methemoglobinemia are at a higher risk of developing heart abnormalities, having a seizure, or even dying prematurely. This disease was found in Kentucky by a single family who have passed the genetic trait onto its family members for some 200 years now.


There is a very good chance you’ll never encounter a case of Kuru, as it is only found in a remote region of New Guinea in the Fore tribe. The disease itself is caused by a type protein called prions, which induce abnormal brain tissue building resulting in progressive and incurable brain damage. This disease itself is one hundred percent lethal, but it is only possible to acquire it these days by… wait for it… eating the brains of an infected victim. Prior to the 1950’s, the Fore tribes’ rituals involved consuming their dead in order to preserve their spirit. This often led to transmission of the disease. With cannibalism outlawed, the disease is practically non-existent today.

Fields Condition

We’re definitely getting into the nitty-gritty of the world’s rarest diseases when you’re talking about Fields Condition. It is a progressive muscle disorder that affected two sisters, Kristie and Catherine Fields. It causes painful muscle spasms up to 100 times a day. The disease is still predominantly a mystery to doctors. However, in its wake, it paralyzed both sisters and cut off their ability to speak. Both sisters now rely on electronic speech machines to communicate.

RPI Deficiency

According to the Journal of Molecular Medicine, Ribose-5 phosphate isomerase deficiency, or RPI Deficiency, is the world’s rarest disease. 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.

Fibrodysplasia Ossificans Progressiva

This is a disorder in which muscle tissue such as tendons and ligaments are gradually replaced by bone (ossified), forming bone outside of the skeleton which then constrains movement. This disease affects about 1 in every 2 million people. This process starts and is quite noticeable in early childhood. This starts with the neck and shoulders and proceeds down the body and into the limbs. Over time this disorder may experience malnutrition due to their eating problems. They may also have a hard time breathing because of the extra bone forming around their rib cage preventing it from expanding. Any trauma to the individual such as a fall or a medical procedure may cause instant muscle swelling and inflammation, and a more rapid ossification of the injured area.

In Conclusion

These are some of the world’s most serious and rare diseases. There isn’t much medical knowledge on these because of the lack of studies and patients.