Harlequin ichthyosis is a painful inherited skin condition characterized by an overproduction of keratin and a subsequent hardening of the skin. Cases have been documented since the 1700s, although until the late 1900s, people with harlequin ichthyosis rarely survived beyond the first week of life, because the condition is associated with a number of complications. This skin disease is very rare, and most likely to occur in the children of people who share a genetic lineage. Worldwide, around 100 people are estimated to be living with harlequin ichthyosis at any given time.
This disease is part of a larger family of skin conditions known as ichthyoses. These diseases are all characterized by the development of thickened, scaly skin. Harlequin ichthyosis is the most severe of these conditions, and it is named after the distinctive diamond shapes of the hardened skin, which resemble the decorations used in harlequin costumes. Individuals with the condition grow as much skin overnight as other people do in 14 days, developing layers of hardened scales and constricted features caused by the tightening and hardening of the skin.
One of the most immediate complications of the disorder is increased susceptibility to bacterial infection. People with this condition have skin which cracks instead of folding, providing numerous sites for bacteria to enter the body. Dehydration is another common problem, as is hyperthermia, because the thickened skin does not allow the body to regulate its temperature very well. People with harlequin ichthyosis are also very susceptible to changes in temperature, thanks to their lack of thermal regulation. Many of them also experience breathing difficulties, because their hardened skin constricts the movement of the rib cage.
This congenital condition is caused by an error on the ABCA12 gene, as genetic testing of patients has revealed. Testing has also uncovered the fact that parents of people with the condition share enough genetic material to suggest that they have common ancestors, and that several patients also appear to share a genetic lineage, suggesting that the condition may be the result of a single genetic mutation. Parents who have a child with the disorder are highly likely to see the condition in future children.
Survival with harlequin ichthyosis hinges on coping with the skin growth and protecting the body. Patients usually spend several hours a day soaking in baths to soften their skin, following with a vigorous scrubbing to remove the outer layers of skin. Heavy use of skin creams and moisturizers to keep the skin hydrated is also important. One patient with this condition, Ryan Gonzalez, is a successful triathlete, proving that it is possible to live and remain active with this condition.