Ichthyosis in Dogs—Congenital Dermatologic Disorder

The skin provides protective functions, such as thermoregulation, resorption, provision of immune responses, storage and sensory functions, which all play an important role in the internal stability of the organism. The skin has 3 major layers: the epidermis, the dermis and subcutis. The outermost protective layer of the epidermis, the stratum corneum, consists of 20 to 30 overlapping layers of anucleate cells, the corneocytes. Ichthyosis is an autosomal recessive congenital skin disease, in which the corneocytes form defects that appear like individual steps of the stratum corneum. Ichthyosis is characterized by excessive scaling over the entire body surface and is not curable; the symptoms can only be alleviated. Several genetic variants have been identified in specific dog breeds: PNPLA1 in the Golden Retrievers, SLC27A4 in the Great Danes, NIPAL4 in the American Bulldogs, TGM1 in the Jack Russel Terriers, ASPRV1 in the German Shepherds, which cause different forms of nonepidermolytic ichthyosis and KRT10 in the Norfolk Terriers, which causes epidermolytic ichthyosis. When classifying breeds of dogs predisposed to ichthyosis, it is necessary to determine the presence of defective genes in the genome of the individual animals involved in mating.