Ichthyosis is a group of genetic skin diseases. Harlequin ichthyosis is the most severe of the lot, and it's very rare -- only around 100 cases have been reported around the world.
Harlequin ichthyosis begins with a gene responsible for lipid transportation. It mutates, hardening a protein called keratin in the outer layer of the skin. That's where the large, pronounced scales come in. The mutated gene is result of a genetic autosomal recessive pattern -- meaning both father and mother passed on the same recessive mutated gene to the child.
The disease doesn't just affect a baby's face -- it also extends to the arms, legs and torso, making it difficult (and often impossible) for the newborn to or move around freely. The hardened scales across the baby's chest make it difficult for him or her to breathe, and the skin's unusual structure causes water loss and leaves the body unable to regulate its temperature. The ridges between the plates of the skin nullify the protection provided by the skin, since the plates don't "seal" together. This introduces a high risk of infection, which is often the cause of death for someone with the disease.
Until fairly recently, the rate of systemic infection for newborns with harlequin ichthyosis was so high that few survived longer than one or two months. Advances in medicine and neonatal care have increased the rate of survival. Retinoids regulate skin cell production and turnover, and they also increase the skin's pliability, meaning that a newborn with harlequin ichthyosis now has the opportunity to blink, move his or her limbs, and eat.
But even with medical advances, it's still tough going. Children with harlequin ichthyosis are at high risk for malnutrition and delayed development due to several factors: difficulty eating, loss of vitamin D and protein through the skin, and less exposure to sunlight due to skin sensitivity.
While better treatment options may become available in the future, the current long-term outlook for those born with this disease is still uncertain.