Harlequin type ichthyosis

Harlequin type ichthyosis, the most severe form of congenital ichthyosis, is characterized by a thickening of the keratin layer in fetal skin. The afflicted child is born with not skin, but massive, diamond-shaped scales. As well, the eyes, ears, mouth, and other appendages can be abnormally contracted. The scaly armor limits the child's movement, and because it is cracked where normal skin would fold, it is useless for skin's primary function – protection. Bacteria and other contaminants easily pass into the cracks and can cause lethal infections.

The term harlequin comes from both the baby's facial expression and the diamond-shaped pattern of the scales, which are caused by severe hyperkeratosis. 17th century entertainers known as jesters, or harlequins, wore costumes with diamond patterns on them, as well as a particular style of face paint. The features of the harlequin fetus mimic this stylized makeup, and their faces are often pulled tight into grim parodies of a clown's smile.

The disease is also known as harlequin ichthyosis, ichthyosis congenita, and keratosis diffusa fetalis. Sufferers are known as harlequin fetuses, harlequin babies, or plain harlequins.

The underlying genetic and biochemical abnormalities that result in harlequin ichthyosis are not yet completely understood. The disease is generally thought to be recessive, so a harlequin fetus will only be born to two parents who carry the gene. The disease can be diagnosed in the womb by way of fetal skin biopsy.

In the past, the disorder was invariably fatal, whether due to dehydration, infection, restricted respiration due to the armored plating, or other related causes. The most common cause of death is systemic infection. However, there have been improvements in care recently, and some children have survived more than the usual few hours. It is thought that with advancing medical care, within a few years, harlequin babies will be able to live for up to a decade. Because of this, and the onset of political correctness, the term harlequin baby is now preferred over harlequin fetus.