Top 10 Rarest Diseases in The World

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Any disease that affects a small percentage of the population is considered a rare disease. An orphan disease is a rare disease that does not have enough market to obtain support and resources for identifying cures for it, unless the government grants economically advantageous conditions for developing and selling such medicines. Because most rare diseases are inherited, they remain present throughout a person’s life, even if symptoms do not show right away. Many rare diseases appear very early in life, and approximately 30% of children with rare diseases die before their fifth birthday. Rare disease day is celebrated on the last day of February month to raise awareness for rare disease and to improve access for the treatment of rare diseases the medicines for rare diseases do not have enough market. Rare disease day 2022 will be celebrated on February 28th.

List of rare disease in the article:

  1. Ribose-5-Phosphate Isomerase Deficiency
  2. Kuru
  3. Progeria
  4. Proteus Syndrome
  5. Foreign Accent Syndrome (FAS)
  6. Robinow Syndrome
  7. Prune Belly Syndrome
  8. Methemoglobinemia
  9. Epidermodysplasia Verruciformis (EV)
  10. Gigantism
  11. Donohue Syndrome

Ribose-5-Phosphate Isomerase Deficiency:

Ribose-5-phosphate isomerase (rpi)​1​ is the most rarest disease in the world known, because only three cases have been reported in twenty-seven years. It is a human disorder caused by mutations in ribose-5-phosphate isomerase (rpi), an enzyme of the pentose phosphate pathway. Characteristics include progressive leukoencephalopathy and high levels of ribitol and D-arabitol in the brain and body fluids. Psychomotor delay, epilepsy, spasticity, cerebellar ataxia, and global developmental delay are all common symptoms of RPI. Ribose-5-phosphate isomerase deficiency currently has no treatment or prognosis.


An advanced stage of Kuru, notice that the child is not even able to stand without help.
Image source: Wikipedia

Kuru​2​ is a very rare and fatal disease of the nervous system. It was very common among the Fore people of Papua New Guinea. Kuru is a type of transmissible spongiform encephalopathy (TSE), which are a group of progressive, often fatal conditions spread by prions that affect the brain and nervous system of many animals, humans, cattle, and sheep. These prions(misfolded proteins) causes tremors and loss of coordination. Kúru itself means trembling, and trembling is one of the symptoms of the disease, other symptoms include sudden outburst of laughter, reason the disease is also called Laughing illness. The sufferers would begin trembling and stumbling and later would lose the ability to stand, and would die eventually because of the disease. It is now widely accepted that the disease spread because of Endocannibalism, cannibalism means eating another human being as food, and endocannibalism means consuming another human being of the same locality as their own. The fore people of Papua New Guinea used to cook and consume the deceased family members as their food and women and children used to eat brain where the infected prions were mostly present and that is why sufferers of the Kuru disease were mainly women and children.


A young girl with progeria. The right bottom is the progeric cell nucleus. The upper left cell is of a normal person.
Image Source: Wikipedia

Also known as Hutchinson-Gilford syndrome​3​ is a type of progeroid syndrome (progeroid syndromes, is a group of rare genetic disorders that imitate physiological ageing and make people look older than they are). Progeria is a disease in which a person will age faster than the average human being, symptoms of HGPS or progeria include insufficient weight gain or inappropriate weight loss, baldness, a large head compared to their body size, reduced range of motion, and, most tragically, a hardening of the arteries in many cases, which raises the risk of heart attack or stroke. Just about hundred cases of Progeria have been reported in medical history, with just a few patients living into their 20s. Although, HGPS is genetically dominant, sufferers rarely live long enough to have children, preventing the disease from being passed down through the generations.

Proteus Syndrome:

Proteus syndrome​4​ is a rare genetic condition that can result in tissue overgrowth affecting all three embryonic lineages. Patients with Proteus syndrome have a higher chance of developing embryonic tumors. In simple words, in Proteus syndrome skin​5​, bones, muscles, fatty tissues, and blood and lymphatic vessels overgrow. It is a rare disease in which infants are born with no visible deformities. Tumors of the skin and bone growths usually occur in early childhood.

Foreign Accent Syndrome (FAS):

Foreign accent syndrome​6​ is a medical condition in which patients develop speech patterns that are perceived as a foreign accent that differs from their native accent without having learned it in the perceived accent’s place of origin. Foreign accent syndrome is most commonly caused by a stroke, but it may also be caused by brain trauma, migraines, or developmental issues. The disorder may be caused by lesions (any damage or abnormal change in the tissue) in the brain’s speech production network, or it could be a neuropsychiatric condition. Though, FAS is not a permanent disorder and is a temporary stage in the recovery from the trauma or stroke but it is still quite shocking how a person starts speaking in a different accent! There was also an unconfirmed report from 2010, that a Croatian speaker gained the ability of speaking fluent German after coming out of coma. Researchers at Oxford University found that some parts of the brain were injured in certain cases of foreign accent syndrome, implying that certain parts of the brain regulate different linguistic functions and that injury may result in altered pitch and/or mispronounced syllables, causing speech patterns to be distorted in a non-specific manner. Some speech disorders, such as mutism (absence of speech), aphasia (inability to understand and form language), dysarthria (disorder caused by an injury in the motor-speech system), agrammatism (inability to use function words), and apraxia of speech (motor-speech disorder), are commonly seen in patients with FAS. This rare syndrome is more common in women than men, and there is no specific treatment.

Robinow Syndrome:

Observe the short toes and feet, The child suffering from the disease can also have some abnormal facial features like, cleft lips.
Image source: Wikipedia

According to NORD, National Organization for Rare Disorders, Robinow syndrome​7​ is a very rare genetic disorder that affects the growth of bones and other body parts. There are two types of this disorder: dominant and recessive, with the former being more common. The characteristics of recessive Robinow syndrome include shortening of the long bones in the arms and legs, short fingers and toes, wedge-shaped spinal bones that contribute to irregular curvature of the spine, fused or absent ribs, short stature, and distinctive facial features that are often referred to as “fetal facies” because the face resembles that of a developing fetus. Underdeveloped genitalia, is also an another symptom of this syndrome, a micropenis with a normally formed scrotum and testes is a commonly seen in males. A smaller clitoris and underdeveloped labia are seen in females, some researches shows some female may also experience vaginal atresia, which means vagina is closed or absent. The labia majora is often underdeveloped as well. All these characteristics are in milder form in dominant Robinow syndrome.

Prune Belly Syndrome:

Prune belly syndrome, aka Eagle-Barrett syndrome​8​ is a genetic birth disorder that affects about one out of every 40,000 babies. Males account for 97 percent of those affected. Prune belly syndrome is a triad of symptoms caused by a congenital urinary system disorder. Signs and symptoms may include lack of abdominal wall muscles​9​, either partially or fully. The abdomen may be covered in wrinkly folds of skin. males with undescended testicles. Prune belly syndrome is characterized by urinary tract abnormalities such as abnormally large ureters, distended bladder, and urine retention and backflow from the bladder to the ureters and kidneys. The exact cause of Prune Belly syndrome is unknown.


An old man suffering from Methemoglobinemia
Image source: Wikipedia

Aka blue-skin disorder, Methemoglobinemia​10​ is a condition of high methemoglobin which is a hemoglobin in the form of metalloprotein. Methemoglobin is unable to bind oxygen, so it is unable to transport oxygen to tissues. Its color is a bluish chocolate-brown. A trace amount of methemoglobin is naturally produced in human blood, but when it is present in excess, the blood turns an abnormally dark bluish brown color. If methemoglobin is high in a person’s body it will causes red blood cells to have a reduced ability to release oxygen to the tissues, which can lead to seizures, heart defects, and premature death. Methemoglobinemia can be treated with supplemental oxygen and methylene blue (a salt used to treat methemoglobin level in the body). The Fugates, a family from Kentucky’s hills known as the “Blue Fugates” or the “Blue People of Kentucky,” are famous for being carriers of a genetic trait that caused methemoglobinemia disorder.

Epidermodysplasia Verruciformis (EV):

Man from Bangladesh suffering from the treeman syndrome. Notice the scaly growth on his hands.
Image source: Wikipedia

Aka treeman syndrome​11​, is an inherited skin condition marked by an abnormal susceptibility to human papillomaviruses or skin warts. These uncontrolled infections cause scaly growths on the hands and feet, which appear between the ages of one year and twenty, though they can also appear in middle age. This disease is caused by an inactivating PH mutation in either the EVER1 or EVER2 genes. These genes control the distribution of zinc in the cell nuclei, many viral proteins need zinc​12​ as a cofactor, and the activity of the EVER1/EVER2 appears to limit viral proteins’ access to cellular zinc stores, limiting their growth. No curative treatment against EV has been found yet. However, to avoid the growth of cutaneous tumors, early diagnosis and excision of tumoral lesions are preferred.


A gigantic man suffering from the human growth hormone.
Image source: Wikipedia

Gigantism​13​ is a disorder in which a person’s growth is abnormal and their height is considerably above normal. Overproduction of growth hormone in infancy causes this syndrome in humans, resulting in individuals ranging in height from 7 to 9 feet. It’s a rare disorder caused by high levels of growth hormone before to the fusion of the growth plate, which normally happens shortly after puberty. The most common cause of this increase is excessive tumor growth on the pituitary gland. Note that gigantism should not be confused with acromegaly which is an adult form of this disorder and causes enlarges body parts like, palms, limbs, forehead, jaws, etc. There are many treatments for gigantism which are not accepted and considered ideal but Pegvisomant is a pharmaceutical drug that has gotten a lot of attention as a potential cure for gigantism. Pegvisomant administration can reduce IGF-I (insulin-like growth factor 1) levels, which can be extremely helpful for patients with pediatric gigantism.

Donohue Syndrome:

Aka leprechaunism, is an extremely rare and severe genetic disorder. This disease is caused a mutation in the INSR gene, which contain genetic information about formation of insulin receptors. Therefore, the affected persons either have decreased insulin receptors or insulins with greatly impaired functionality. Insulin receptor impairment causes severe insulin resistance​14​, which results in an inability to control blood glucose levels. leprechaunism can lead to conditions such as hyperglycemia (high blood glucose levels), hypoglycemia (low blood glucose level). Other facial and physical signs and symptoms can include large mouth, thick lips, excessive body hair growth. Gender features include enlarged clitoris and breasts in females and enlarged penis in males. Leprechaunism patients do not live longer but there are a few who known to have lived longer. There is no cure for Donohue syndrome currently.


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