Mutations in over 40 different genes can cause ichthyosis, and multiple gene mutations are generally present in people with genetic forms of the condition, National Institute of Arthritis and Musculoskeletal and Skin Diseases explains. Parents sometimes carry the mutations and pass them on to offspring, but the condition can also arise from spontaneous mutations in the sperm or eggs of the parents before or shortly after conception. The exact symptoms of ichthyosis depend on which genetic mutations cause the condition.
There are many forms of ichthyosis, including harlequin ichthyosis and lamellar ichthyosis, each caused by mutations in different genes, according to Genetics Home Reference. A mutation in the gene ABCA12 causes harlequin ichthyosis by limiting or completely stopping the production of an essential skin protein. This protein helps the skin move lipids up to the surface of the skin. The lack of proper lipid transport disrupts the development of the epidermis, so that the skin forms hard, thick scales.
A mutation in the TGM1 gene causes about 90 percent of lamellar ichthyosis, but mutations in other genes cause the rest of the cases, Genetics Home Reference explains. Mutations in these genes disrupt the formation of proteins that help form the surface layer of the skin. This causes the skin to form large, dark, plate-like scales and lessens its ability to help regulate temperature and protect against infection.