Harlequin-type ichthyosis

Not to be confused with Harlequin syndrome.

Harlequin-type ichthyosis is a rare, severe genetic disorder affecting the skin, specifically characterized by thick, armor-like scales covering the body. It is the most severe form of congenital ichthyosis.

Introduction

Harlequin-type ichthyosis derives its name from the Harlequin character in Italian commedia dell'arte due to the diamond-shaped scales typically seen in affected individuals. This disorder significantly affects the skin's barrier function, leading to a host of potential complications.

Genetics

Harlequin ichthyosis results from mutations in the ABCA12 gene, which provides instructions for producing a protein crucial for normal skin development. This protein plays an essential role in transporting lipids, which are necessary for the development of the skin's protective barrier. The mutation in the ABCA12 gene prevents the protein from effectively transporting these lipids, leading to the skin abnormalities seen in Harlequin ichthyosis.

Clinical Features

The skin of babies with Harlequin ichthyosis is covered in thick, diamond-shaped plates separated by deep cracks (fissures). These skin abnormalities affect the shape of facial features and limit movement of the arms and legs. Restricted movement can lead to fused fingers and toes (syndactyly) and abnormalities of the arms and legs.

Furthermore, the tightness of the skin pulls around the eyes and mouth, forcing the eyelids and lips to turn inside out, revealing the red inner linings. These abnormalities lead to feeding and breathing difficulties, as well as susceptibility to infection.

Diagnosis

Diagnosis of Harlequin ichthyosis can be made prenatally through ultrasound or genetic testing, or after birth by observing the child's clinical presentation. Confirmatory diagnosis is typically done through genetic testing, confirming the presence of mutations in the ABCA12 gene.

Management and Treatment

There is no cure for Harlequin ichthyosis, and treatment is primarily supportive. Management involves intensive skincare, including regular application of emollients to prevent cracking and infections and to improve the skin's flexibility.

Additionally, systemic retinoids, such as isotretinoin or acitretin, can be used to reduce the thickness of the skin's scales. Other supportive treatments can include nutritional support, physiotherapy, and eye care.

Prognosis

Historically, Harlequin ichthyosis was considered lethal. However, advances in neonatal care and the early initiation of systemic retinoids have improved survival, with affected individuals now living into adulthood.

Harlequin-type ichthyosis Resources
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NIH genetic and rare disease info

• NIH info on Harlequin-type ichthyosis

Harlequin-type ichthyosis is a rare disease.