Babies with harlequin ichthyosis are typically born prematurely. When they’re born, their bodies are covered in thick, platelike scales of skin. Skin tightness causes the scales to form deep cracks (fissures). The tightness also pulls the skin around your baby’s eyes and mouth, causing their eyelids and lips to turn inside out. It also pulls on the skin of your baby’s chest and abdomen, making it difficult to breathe and eat. Other symptoms may include:

• Flat nose.
• Ears fused to their head.
• Small, swollen hands and feet.
• Abnormal hearing.
• Frequent respiratory infections.
• Decreased joint mobility.
• Low body temperature.

Causes

A genetic variant (genetic mutation) in the ABCA12 gene causes harlequin ichthyosis. The ABCA12 gene gives your body instructions for making a protein that’s vital for the development of healthy skin cells. This protein has an important role in transporting fats (lipids) to the outermost layer of your skin (epidermis), producing a barrier.

If you have harlequin ichthyosis, you have abnormally small amounts of the ABCA12 protein or none at all. This disrupts the normal development of your epidermis, which leads to the severe symptoms that the condition produces.

You inherit harlequin ichthyosis in an autosomal recessive manner, which means you receive both copies of the affected gene — one from each parent. The parents are both carriers of the mutated gene but typically don’t show symptoms of the condition.

Diagnosis and Tests

The diagnosis of harlequin ichthyosis relies on a physical examination of the patient and genetic laboratory investigations.

Genetic testing for a loss of function mutation in the ABCA12 gene is the most specific diagnostic test for harlequin ichthyosis.

• Mutations in the gene may cause impaired transport of lipids in the skin and shrunken versions of proteins responsible for skin development.
• Less severe mutations result in a collodion membrane and congenital ichthyosiform erythroderma-like presentation.

Skin biopsy shows a very thickened stratum corneum, parakeratosis, and hypergranulosis.

Treatment

There is no cure for harlequin ichthyosis, and treatment is centred around protecting the skin and preventing infection.

After birth, the thick plate-like outer layer of skin eventually splits and peels, leaving the vulnerable inner layers of the dermis exposed. Most harlequin infants will need one-on-one nursing care for the first several weeks of life. Antibiotic treatment may also be necessary to prevent or treat infection during this time.

Softening emollients, especially those containing urea, salicylic acid or alpha hydroxy acids, are particularly effective when applied after bathing while the skin is still moist. These products work to keep the skin moisturised and pliable while preventing the cracking and fissuring that can lead to secondary bacterial infection.

Early systemic treatment with oral retinoids (eg, acitretin or isotretinoin) has also been shown to heal skin fissures, soften or resolve plate-like scales, and improve overall survival