Harlequin ichthyosis is a rare disorder where affected infants are covered with thick, scaly plates of skin. This skin can’t protect the body in the way healthy skin can, leading to dehydration and serious infection. Breathing, eating and movement are restricted, resulting in other serious medical complications.
There are a family of ichthyosis disorders. Harlequin ichthyosis is the most severe, and is often fatal in early life. It is also the rarest in the group, though the precise number of cases hasn’t been recorded. There are medical therapies which can help manage the disorder, but there is currently no way of reversing the mutation.
The Gene Involved in Genetic Disorder
The gene involved in harlequin ichthyosis is located on chromosome 2. It is called “ATP-binding cassette, sub-family A (ABC1), member 1”, or ABCA12. It provides instructions for making the ATP-binding cassette (ABC) transporter protein, which is important in skin development. When the ABCA12 gene is mutated, the protein is abnormal or missing, and harlequin ichthyosis results.
Inheritance of Genetic Disorder
People inherit genes from their mothers and fathers. When a disorder is autosomal recessive, the affected person’s cells will have mutated gene copies contributed from both biological parents. When someone has only one mutated gene copy in each cell, they are said to ‘carry’ the disorder and can pass it to their children.
Harlequin ichthyosis is inherited in the aforementioned pattern. When both parents carry the mutated gene copy, the chances of the child being affected are the following for each pregnancy:
- A 1 in 4 (25%) chance of having a child affected with harlequin ichthyosis.
- A 1 in 2 (50%) chance of having a child who carries harlequin ichthyosis.
- A 1 in 4 (25%) chance of having a child who is completely unaffected.
Genetic Testing and Genetic Disorder
Harlequin ichthyosis is usually diagnosed from its signs and symptoms, but molecular genetic, prenatal and carrier testing are all possible. Health professionals called genetic counselors are trained to offer genetic health information impartially. Those concerned about harlequin ichthyosis may be able to access these services.
Visit the Foundation for Ichthyosis and Related Skin Types website for more information and support, including details on accessing specialist therapies. Read Understanding Genetic Consultation, Understanding Genetic Counseling and Understanding Genetic Testing in Healthcare for more information on genetic testing and genetics services.
Sources
“Autosomal Recessive Congenital Ichthyosis”, last revision: 19th November 2008, GeneReviews (NCBI) website, accessed: 18th January 2011, authors: Bale, Sherri and Richard, Gabrielle.“Harlequin ichthyosis”, Foundation for Ichthyosis and Related Skin Types website, accessed: 18th January 2011, no author specified.
“Harlequin ichthyosis”, reviewed: November 2008, Genetics Home Reference website, accessed: 18th January 2011, no author specified.
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