Retinitis pigmentosa is a group of rare inherited genetic disorders caused by one of more than 70 genes

Thousands of genes exists in our cells and each of them perform unique functions. Small changes (mutations) in the nature of gene can significantly affected the individual. Here, 99Science takes you through on some uncommon genetic disorders that you might not have heard of.

List of  rare genetic disorders

Proteus Syndrome

Proteus Syndrome is a rare genetic disorder in which bones, skin, and other tissues are overgrown. The disorder originates from a mutation in a gene called AKT1 which controls cell growth. There is a disparity in the growth of cells in patients with proteus syndrome. This difference in the sizes of cells causes a disfigured tissue.

A person Proteus Syndrome- an uncommon genetic disorder

Image Source: Wikipedia


Famously known as ‘lobster claw hand’ or ‘split hand malformation’, individuals with this disorder have a cleft where the middle finger or toe should be. This genetic results in mutations in chromosome 7.

A person with ectrodactyly- an uncommon genetic disorder

Image Source: Wikipedia


Polymelia is a disorder in which an organism has more than the usual number of limbs. It results from a partially absorbed conjoined twin. It also occurs in animals.

A black cow with polymelia- an uncommon genetic disorder

Image Source: Wikipedia


Anencephaly is a disorder marked by the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. The cerebral hemispheres are the main brain parts affected.

An illustration of a person with anencephaly- an uncommon genetic disorder

Image Source: Wikipedia

Feet facing backwards

The picture below is of Wang Fang, a young woman from China. She was born with a rare where her feet faced backwards. Wang Fang has lived a healthy and normal life as any person.

A smiling chinese woman with a feet facing forward- an uncommon genetic disorder

Image Source: nydailynews


Scientists still do not know the exact cause of this disorder. The skin of the individual becomes thick and lumpy and a bony lump grows on the patient’s forehead. Experts suggest that the disorder is a possible combination disorders like neurofibromatosis type I and Proteus syndrome.

A picture of the back of a person with neurofibromatosis- an uncommon genetic disorder

Image Source: Gudhealth

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Diprosopus is an extremely rare hereditary disorder in which parts (or entire face) are duplicated. It is also called craniofacial duplication. The abnormal function of the protein SSH (Sonic hedgehog) leads to this disorder.

A baby with diprosopus- an uncommon genetic disorder

Image Source: Wikipedia

Harlequin ichthyosis

Harlequin ichthyosis is a rare disorder of the skin. Affected individuals have thick plates of skin separated with deep red cracks all over their bodies.

A baby with harlequin ichthyosis- an uncommon genetic disorder

Image Source: Impocity


When the embryo fail to properly divide and the tracks of the eyes transform into two hollows, Cyclopia results. It is much more common in animals than humans.

An infant with cyclopia- an uncommon genetic disorder

Image Source: Leilajouybari

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Cutaneous horn

This is also called cornu cutaneum and is characterised by an unusual skin tumor with a horn-like outgrowth. The horns are small but they can get very big. The horn of a french woman measured 10 inches.

A person with a cutaneous horn on the head

With advances in genetics and biotechnology, some of these disorder could be corrected in future.

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