Harlequin ichthyosis is a keratinization disorder due probably to cutaneous lipid anomalies. It is characterized by hyperkeratosis forming plates and grooves that look like Harlequin's costume. Infants with Harlequin ichthyosis are usually born prematurely and are encased in thick, hard, armor-like plates of cornified skin separated by deep fissures that severely restrict movement. Most infants with Harlequin ichthyosis are born as collodion babies that are born with a taut, shiny, translucent or opaque membrane that encases the entire body and lasts for days to weeks. The taut skin results in deformation of facial features and microcephaly. Affected infants are at risk for life-threatening complications in the postnatal period, such as respiratory distress, dehydration, electrolyte imbalance, temperature instability, feeding problems, and bacterial infections, often with fatal consequences. They usually die within the first weeks of life. However, improved survival into childhood and adolescence has been achieved with intense supportive care and systemic retinoid therapy in the neonatal period. Patients who survive manifest a debilitating, persistent ichthyosis.
Prenatal diagnosis for malignant keratoma had been performed by fetal skin biopsy and electron microscopic observation at 19-23 weeks estimated gestational age. Harlequin ichthyosis is very rare with an incidence of about 1 in 300.000 births.