Answer by
LeheckaG (1826)
Harlequin-type ichthyosis is caused by a genetic-disorder, either inherited or a mutation;
milder cases might be caused by a Vitamin-A deficiency.
In severe cases, the skin's keratin-layer thickens and appears like diamond-shaped scales.
It can be diagnosed either via amniocentisis of by modern (3D) ultra-sound techniques.
Isotretinoin(Isotrex) can be used to treat it; previously victims died within a few days.