Harlequin Ichthyosis

What is harlequin ichthyosis?

Harlequin ichthyosis is a severe genetic disorder that mainly affects the skin. Infants with this condition are born with very hard, thick skin covering most of their bodies. The skin forms large diamond-shaped plates separated by deep cracks (fissures). These skin abnormalities affect the shape of the eyelids, nose, mouth, and ears, and restrict movement of the arms and legs. Restricted movement of the chest can lead to breathing difficulties and respiratory failure.

The skin normally forms a protective barrier between the body and its surrounding environment. The skin abnormalities associated with harlequin ichthyosis disrupt this barrier, making it more difficult for affected infants to control water loss, regulate their body temperature, and fight infections. Infants with harlequin ichthyosis often experience an excessive loss of fluids from the body (dehydration) and develop life-threatening infections during the newborn period.

How common is harlequin ichthyosis?

Harlequin ichthyosis is very rare; its exact incidence is unknown.

What genes are related to harlequin ichthyosis?

Mutations in the ABCA12 gene cause harlequin ichthyosis.

The ABCA12 gene makes a protein that is essential for the normal development of skin cells. This protein appears to play a major role in the transport of lipids (fats) in the outermost layer of skin (the epidermis). Some mutations in the ABCA12 gene prevent the cell from making any ABCA12 protein. Other mutations lead to the production of an abnormally small version of the protein that cannot transport lipids properly. The loss of functional ABCA12 protein disrupts the normal development of the epidermis, preventing the skin from forming an effective barrier and resulting in the hard, thick scales characteristic of harlequin ichthyosis.

How do people inherit harlequin ichthyosis?

This condition is likely inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.

Where can I find information about treatment for harlequin ichthyosis?

These resources address the management of harlequin ichthyosis and may include treatment providers.

• Gene Review: Autosomal Recessive Congenital Ichthyosis
• Genetic Alliance

You might also find information on treatment of harlequin ichthyosis in Educational resources and Patient support.

Where can I find additional information about harlequin ichthyosis?

You may find the following resources about harlequin ichthyosis helpful. These materials are written for the general public.

• MedlinePlus - Health informationHealth Topic: Skin Conditions
• Educational resources - Information pages (4 links)
• Patient support - For patients and families (2 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• ClinicalTrials.gov - Linking patients to medical research
• PubMed - Recent literature
• OMIM - Genetic disorder catalog

What other names do people use for harlequin ichthyosis?

• Harlequin baby syndrome
• HI
• Ichthyosis Congenita, Harlequin Fetus Type

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about harlequin ichthyosis?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center.
• Submit your question to Ask the Geneticist.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding harlequin ichthyosis?

autosomal ; autosomal recessive ; cell ; dehydration ; epidermis ; fetus ; gene ; ichthyosis ; incidence ; infection ; lipid ; mutation ; protein ; recessive ; respiratory ; sign ; symptom ; syndrome

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.