5 of the World's Rarest Skin Conditions

Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are two forms of the same serious skin condition that causes skin and even the lining of internal organs to shed and fall off. The two forms are so closely associated that doctors often group them together, referring to them as SJS/TEN.

Often starting with flu-like symptoms, SJS/TEN then causes skin to develop painful rashes and blisters. The top layer of skin then actually separates and falls off the body. If the patient's body loses less than 10 percent body surface area, it is classified as SJS [source: NIH]. Anywhere from 10 to 30 percent loss is considered overlapping SJS/TEN, and more than 30 percent is classified as TEN [source: Parrillo].

People usually develop SJS/TEN as a result of a reaction to a drug. The drugs include non-steroid anti-inflammatory drugs, Allopurinol, Phenytoin, Carbamazepine, barbiturates, anticonvulsants and sulfa antibiotics [source: Skin Association]. The reaction can start a week to two weeks after first taking the drug [source: NIH]. But in about a quarter of all cases, doctors have been unable to pinpoint what causes the onset of SJS [source: NIH].

Each year, the condition affects only a few people per million [source: Physorg.com]. Though often curable depending on the severity, SJS/TEN can be life-threatening and usually requires hospitalization. Doctors may attempt to treat the condition with intravenous immunoglobulins, as well as antibiotics for skin infections and corticosteroids for inflammation [source: NIH].

This next skin condition is not nearly as serious as the one on the previous page and is never life-threatening, but it's rare and unusual just the same.

If you think you've got sensitive skin, you might think again after hearing about this condition. People with dermatographia have extremely sensitive skin, where even the slightest scratch or rubbing can cause the skin to react with raised red lines. It affects perhaps up to 5 percent of the population [source: Mayo Clinic]. Slight scratches will cause skin to swell and perhaps develop hive-like welts. The skin will often begin to itch uncomfortably.

Just to illustrate how severe it can be, people with this condition can literally write on their skin by lightly scratching it with their fingernails. Within minutes, distinct raised lines will appear, showing their writing with remarkable clarity. For this reason, the condition is also known as "skin writing."

Other things that can cause skin reactions are chafing from clothes as well as exposure to heat, cold or sunlight, or even experiencing emotion [source: Mayo Clinic]. Doctors aren't sure what causes dermatographia, but some speculate that it is some kind of allergic reaction.

Although the redness and welts will go away with time (30 minutes to a few hours), the symptoms can be painful, which is why doctors might recommend anti-histamines. The Mayo Clinic also suggests staying hydrated and using skin moisturizer, because dry skin only exacerbates the problem [source: Mayo Clinic].

Harlequin ichthyosis affects newborns -- they are born with thick, hard plates of skin covering their body. These plates are separated by deep cracks.

This extremely rare condition makes it difficult for the affected babies to control water and fluid loss, resulting in severe dehydration. Babies with harlequin ichthyosis also have trouble moving, breathing, fighting off infection and regulating their body temperature [source: NIH]. With such complications, it is very common for an infant to die within weeks after birth.

Doctors believe that harlequin ichthyosis is a genetic disorder where a mutation in the ABCA12 gene affects the development of the epidermis [source: NIH]. More than 100 cases have been reported around the world [source: Prendiville].

Though some babies have been known to survive with the condition, they require intensive care in an incubator where such things as temperature and bodily fluids can be monitored and nutrients can be quickly replaced. Even for patients who can survive past infancy, harlequin ichthyosis is incurable, and they would have to struggle with it their entire life.

One person surviving the disease into his teens has said he hangs on to life by consuming 7,500 calories a day to make up for the lost nutrients of shedding skin 10 times faster than the average person and moisturizes his skin seven times a day [source: 10news].

Most people know to wear sunscreen to avoid sunburn and to protect against skin cancer if they're planning to be in the sun for any extended period of time. But can you imagine being so sensitive to ultraviolet (UV) light that you have to avoid sunlight through windows or even florescent lights?

Such is life for those who have xeroderma pigmentosum (XP), which happens to be about only 1 in every 250,000 people in the United States [source: XPmutations.org]. The dangers of sunlight to their skin are the same as for the rest of us -- that is, damage from UV light -- except that their skin is extremely sensitive to it.

Symptoms include not only sunburn and blistering (after little sun exposure), but also light and dark skin patches. Skin can also become so thin that blood spots and vessels are visible [source: New Zealand Dermatological Society]. As you might have guessed, such sensitivity almost inevitably leads to the development of skin cancer.

As a genetic disorder, XP occurs as a result of a faulty DNA repair system. Most people's bodies can repair DNA damage caused by sun exposure, but those with XP cannot. Although doctors can treat the symptoms, there is no known cure. It is so bad that children growing up with XP usually develop skin cancer and die by the time they become young adults [source: NIH].

This next condition sounds like a rumor you'd hear on the playground as a child, but it is very true. People who suffer from argyria develop gray or even blue skin. As we mentioned earlier, the "Blue Man" from Barnum and Bailey had argyria. Pictures of people who suffer from the condition at first appear photoshopped.

Though it seems out of this world, people who ingest or are exposed to large amounts of silver over a long period of time will develop this condition. Development from skin exposure can happen to silver mine workers, or those who work with silver in manufacturing or developing photographs. Some have taken silver supplements because they were advertised as a cure an array of ailments, such as arthritis, diabetes or even AIDS. Others are believed to have developed the condition from the silver used in dental fillings [source: New Zealand Dermatological Society].

Argyria is a permanent condition without a clear cure as of yet. Although silver has been known to have more dangerous toxic effects on the body, the only negative side effect people with argyria will usually have is the change in skin pigmentation [source: Padlewska].