Unfortunately, living organisms, including humans, are often marred with diseases during their lifetime. There are over 25,000 diseases, most of which scientists and medical professionals have managed to diagnose and find treatment for. On the other hand, there are extremely rare disorders, some of which remain unknown to humankind. Of the about 7,000 diseases categorized as rare, only approximately 400 have an effective treatment. As such, there is a Rare Disease Day, usually held on the last day of February, which recognizes this fact and more. With some having less than 100 reported cases worldwide, here is a list of the rarest diseases known to humans.

1. Hematidrosis

Sometimes referred to as hemidrosis, haematidrosis, or hematohidrosis, hematidrosis is an ultra-rare condition, which causes the patient to sweat blood. It results when the capillary blood vessels feeding the sweat glands rupture. Symptoms include oozing blood from the umbilicus, nails, forehead, and other surfaces of the skin.

Vicarious menstruation, bloodstained tears, and frequent nosebleeds can also be a result of hematidrosis. For Christians, hematidrosis is the same condition that Jesus suffered while praying in the garden of Gethsemane moments before his crucifixion.

2. Mitchell Syndrome (MITCH)

A teenager named Mitchell Herndon suffered from a very rare disease that only two other people had been diagnosed with before. The neurological disorder robbed him of his ability to walk, hampered his eyesight, and affected his hearing.

At the time of Herndon’s diagnosis, the condition didn’t have a name, so doctors named it the “Mitchell Disease” when he died. He requested that his body be donated for further studies, a request that was honored by his parents. He died days before a potential life-saving drug would have been available to him – he was only 19.

3. Fatal Insomnia

As its name suggests, fatal insomnia is characterized by trouble sleeping. It is an ultra-rare neurodegenerative prion disease that starts out with gradual sleeping problems. As it advances, the patient succumbs to agrypnia excitata (complete insomnia), which then results in dementia, coordination problems, and speech issues.

4. Kleine-Levin Syndrome (KLS)

Kleine-Levin syndrome is probably the opposite of fatal insomnia. It is a rare disease characterized by excessive sleeping (hypersomnia). Patients can also exhibit hypersexuality, compulsive eating behavior, and cognitive & behavioral disturbances. A girl from Pennsylvania once slept for 64 days after suffering an episode of KLS.

5. Kuru (Laughing Disease)

Popularly known as the laughing disease (the disorder’s main symptom), Kuru is an extremely rare disease that thrived in the 50s and 60s among the Fore people inhabiting the highlands of New Guinea. Kuru, which translates to “trembling,” was transmitted through funerary cannibalism, which was popular among the Fore tribe.

6. Urbach-Wiethe Disease

Since its discovery, only about 400 cases of Urbach-Wiethe disease have been reported. The disorder’s symptoms vary significantly from one patient to the other. Common ones include having a hoarse voice, scarring on the skin, and poor wound healing. Interestingly, Urbach-Wiethe disease destroyed the amygdala (the part of the brain responsible for processing emotions) of a woman known as SM, making her fearless and anxiety-free. SM doesn’t fear snakes or react to scary movies; nothing gives her chills.

7. Lipodystrophy

Lipodystrophy is a rare and bizarre medical condition that causes the patient to lose fat from specific body parts while gaining in others. The inconsistency always affects how an individual’s appears; they mostly appear way older than they really are. Zara Hartshorn is a famous example of an individual suffering from lipodystrophy. When she was only 15, she looked like a person in her 40s or 50s. Zara was forced to undergo a facelift as she was often called “a granny” by her peers.

8. Cherubism

With approximately 200 cases of the condition reported worldwide (primarily boys), cherubism is a rare disorder that causes the lower portion of the face to become prominent. It occurs when the mandible loses its bone cavity, which the body instinctively replaces with excessive fibrous tissue. Usually, cherubism heals by itself as the child grows. However, in extremely rare cases, it may persist into adulthood.

9. Dublin-Johnson Syndrome

First described by pathologists Isadore Dubin and Frank Johnson in 1954, Dublin-Johnson syndrome is a very rare autosomal recessive, benign disorder often caused by a separate increase of conjugated bilirubin in the serum. Jaundice is one of the most common symptoms of Dublin-Johnson syndrome; more than 80% of Dublin-Johnson syndrome patients have jaundice. Abnormality of the gastric mucosa, fatigue, and fever can also be indicators of Dublin-Johnson syndrome.

10. Maple Syrup Urine Disease

The Maple Syrup Urine Disease (MSUD) is a rare autosomal recessive metabolic disorder that affects how the patient’s body processes some amino acids. It is characterized by urinating urine with a maple syrup order, hence the name. It can be fatal.

11. Stevens-Johnson Syndrome (SJS)

Stevens-Johnson syndrome is a form of severe skin reaction characterized by peeling and blistering of the skin, leading to painful raw areas. It usually starts with flu-like symptoms and headache. In the end, complications from SJS can lead to sepsis, multiple organ failure, dehydration, and pneumonia.

There are different stages of SJS diagnosis:  when less than 10% of the skin is involved, it is considered mild. When 10-30% of the skin is affected, it is categorized as intermediate, while anything above 30% is considered Toxic Epidermal Necrolysis (TEN).

12. Zimmermann-Laband Syndrome

Sometimes referred to as Laband’s syndrome, the Zimmermann-Laband syndrome (ZLS) is an ultra-rare genetic disease mainly characterized by distal phalanges, coarse facial appearance, hypo/aplastic nails, and gingival fibromatosis (GF). Although it is a very rare disease, a patient with the disorder has a 50% chance of passing it to their offspring.

13. Multiple Epiphyseal Dysplasia (MED)

Commonly known as Fairbank’s disease, multiple epiphyseal dysplasia (MED) is a rare genetic disorder that affects how the ends of bones grow. It is a type of non-rhizomelic dwarfism that flattens and fragments the epiphyses. A dominant form of the disease occurs in 1 in 10,000 births. Danny DeVito, a filmmaker known for his role in “It’s Always Sunny in Philadelphia,” was diagnosed with Fairbank’s disease. He stands at 4 feet 10 inches.

14. Fibrodysplasia Ossificans Progressiva (FOP)

This is a rare musculoskeletal condition that replaces the patient’s skeletal muscles, tendons, and ligaments with bones, thereby “locking” them in one place. Unfortunately, any attempts to remove the extra bone, be it surgically, results in more rapid bone buildup, causing more injuries and damage.

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Last Update: May 1, 2024