Harlequin-type ichthyosis

Harlequin-type ichthyosis is a genetic disorder that results in thickened skin over nearly the entire body at birth. The skin forms large, diamond/trapezoid/rectangle-shaped plates that are separated by deep cracks. These affect the shape of the eyelids, nose, mouth, and ears and limit movement of the arms and legs. Restricted movement of the chest can lead to breathing difficulties. These plates fall off over several weeks. Other complications can include premature birth, infection, problems with body temperature, and dehydration. The condition is the most severe form of ichthyosis (except for syndromes that include ichthyosis, for example, Neu–Laxova syndrome), a group of genetic disorders characterised by scaly skin.

Harlequin-type ichthyosis is caused by mutations in the ABCA12 gene. This gene codes for a protein necessary for transporting lipids out of cells in the outermost layer of skin. The disorder is autosomal recessive and inherited from parents who are carriers. Diagnosis is often based on appearance at birth and confirmed by genetic testing. Before birth, amniocentesis or ultrasound may support the diagnosis.

There is no cure for the condition. Early in life, constant supportive care is typically required. Treatments may include moisturizing cream, antibiotics, etretinate or retinoids. Around half of those affected die within the first few months; however, retinoid treatment can increase chances of survival. Children who survive the first year of life often have long-term problems such as red skin, joint contractures and delayed growth. The condition affects around 1 in 300,000 births. It was first documented in a diary entry by Reverend Oliver Hart in America in 1750.