20 Diseases You’ve Probably Never Heard Of

You’re about to discover some of the rarest and most bizarre diseases in the world. These conditions may seem surreal, but they are real for those suffering from them.

Alien Hand Syndrome

AHS is a rare neurological disorder causing one hand to act independently. It often results in uncontrolled, unintended actions by the hand.

Congenital Insensitivity to Pain

This rare disease causes people to not feel pain, leading to unnoticed injuries. Seems a blessing, but it can cause serious complications.

Geographic Tongue

Also known as benign migratory glossitis, this disease causes moving patches on the tongue, creating a map-like appearance. Though harmless, it can cause discomfort or altered taste.


This genetic disorder, Trimethylaminuria, causes a fish-like body odor and related social challenges. Learn more

Capgras Delusion

Capgras delusion is a rare psychiatric disorder causing individuals to believe their loved ones are replaced by imposters, leading to distress and requiring long-term treatment.

Foreign Accent Syndrome

This rare neurological disorder leads individuals to suddenly adopt a foreign accent even without exposure to its region. Causes may include brain injuries and strokes, but remain unclear.

Exploding Head Syndrome

A type of parasomnia, this condition causes individuals to experience loud and sudden noises in their head as they are falling asleep or waking up. 

Alice in Wonderland Syndrome

This neurological disorder, named after Lewis Carroll's novel, distorts body and environmental perceptions, causing visual alterations.


"Face blindness" or prosopagnosia, affects a person's ability to recognize and remember faces, even their own, often relying on other cues for identification.


Synesthesia is when one sensory experience induces another, like seeing colors or tasting flavors while listening to music.

Pantothenate Kinase-Associated Neurodegeneration

This rare genetic disorder leads to movement issues, speech problems, & visual loss. Usually appearing in childhood, it rapidly progresses.

Ondine’s Curse

Congenital Central Hypoventilation Syndrome, a potentially fatal condition, affects automatic breathing, often causing sufferers to stop breathing during sleep.

Paraneoplastic Pemphigus

This autoimmune blistering disorder is a painful sores on the skin and mucous membranes. It is often associated with malignancies like lymphomas and leukemias.

Stiff Person Syndrome

A neurological disorder, Stiff Person Syndrome features muscle stiffness and functional impairment. The condition can also cause muscle spasms and functional disability.

Erdheim-Chester Disease

This rare non-Langerhans cell histiocytosis mainly affects adults and leads to organ damage due to excessive histiocytes production.


Alkaptonuria is a rare disorder causing urine to turn black upon air exposure and skin darkening due to homogentisic acid buildup in the body.

Hyper Igm Syndrome

'Hyper IgM Syndrome is an immunodeficiency disorder leading to a decreased ability to fight infections, often causing recurrent infections and potential autoimmune diseases.'

Fibrodysplasia Ossificans Progressiva

Fibrodysplasia Ossificans Progressiva is a connective tissue disease that causes soft tissues to become ossified, turning them into bone over time gradually.

Ocular Cicatricial Pemphigoid

A form of autoimmune conjunctivitis, this disease can lead to scarring of the conjunctiva and potentially cause blindness.

Paraneoplastic Neurologic Syndromes

Disorders are caused by abnormal immune response to a neoplasm, leading to symptoms like difficulty walking, swallowing, memory loss etc.

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