Harlequin-type ichthyosis (also harlequin ichthyosis, ichthyosis congenita, Ichthyosis fetalis or keratosis diffusa fetalis), a skin disease, is the most severe form of congenital ichthyosis, characterized by a thickening of the keratin layer in fetal human skin. In sufferers of the disease, the skin contains massive, diamond-shaped scales, and tends to have a reddish color. In addition, the eyes, ears, mouth, and other appendages may be abnormally contracted. The scaly keratin greatly limits the child's movement. Because the skin is cracked where normal skin would fold, it is easily pregnable by bacteria and other contaminants, resulting in serious risk of fatal infection.
Sufferers are known as harlequin fetuses, harlequin babies, or harlequins.
The harlequin-type designation comes from both the baby's apparent facial expression and the diamond-shape of the scales (resembling the costume of Arlecchino), which are caused by severe hyperkeratosis. The disease can be diagnosed in the uterus by way of fetal skin biopsy or by morphologic analysis of amniotic fluid cells obtained by amniocentesis. In addition, doctors can now usually recognize common features of the disease through ultrasound, and follow up with 3D ultrasound can diagnose the condition.
"On Thursday, April 5, 1750, I went to see a most deplorable object of a child, born the night before of one Mary Evans in 'Chas'town. It was surprising to all who beheld it, and I scarcely know how to describe it. The skin was dry and hard and seemed to be cracked in many places, somewhat resembling the scales of a fish. The mouth was large and round and open. It had no external nose, but two holes where the nose should have been. The eyes appeared to be lumps of coagulated blood, turned out, about the bigness of a plum, ghastly to behold. It had no external ears, but holes where the ears should be. The hands and feet appeared to be swollen, were cramped up and felt quite hard. The back part of the head was much open. It made a strange kind of noise, very low, which I cannot describe. It lived about forty-eight hours and was alive when I saw it."
At least 100 cases have been reported worldwide in modern times. Neither gender nor ethnicity seem to affect the likelihood of a child having the disorder. A disproportionately high number of children have consanguineous parents. Those from families with a history of severe skin disorders may have a higher risk of birthing a harlequin child.
They are extremely susceptible to changes in temperature due to their armor-like skin, which prevents normal heat loss. This can result in hyperthermia. Their respiration is also restricted by the skin, which impedes the chest wall from expanding and drawing in enough air. This can lead to hyperventilation and respiratory failure. Harlequins are often dehydrated, as their plated skin is not well suited to keeping water in.
A Real Families documentary broadcast on ITV1 in the United Kingdom in 2005 (and later rebroadcast in other countries) showed the lives of two pairs of sisters afflicted with the condition: Lucy and Hannah Betts (ages 18 and 15), and Dana and Lara Bowen (ages 8 and 1½). The girls all went through a daily routine of getting up early in the morning and bathing for two hours to soften the skin, scrubbing hard to remove as much of the hard extra skin as possible, and then covering their entire bodies in a thick layer of moisturiser. A second and third "creaming" as they called it had to be performed in the afternoon and at bedtime to soften the skin. Even with this treatment a thick layer of hyperkeratotic skin covered them and they were plagued with infections. Scales on the inside of the eyelids had blinded one of Lucy's eyes and left the other eye with 10% vision. Hannah Betts also suffers from cerebral palsy. Their skin was said to grow at fourteen times the normal rate. Vacuuming the carpets was necessary at least a couple of times a day to remove the shed skin.. A documentary on Five in 2008 showed the same children three years later after major advances in medical technology.
The children were said to be four of just seven in the United Kingdom, Lucy being the longest surviving of any such child in the country ever. The chances of suffering from the condition were given as roughly one in a million in general. These figures would indicate that one in 500 people have the recessive allele, giving a one-in-250,000 chance of two unrelated people bringing these alleles together, and finally there being a one-in-four chance of these alleles being brought together and causing the condition.
The chances of any one person with the disease mating with an unaffected person to produce a child who is also a sufferer would be about 1 in 2000.