LI can be caused by harmful changes in several genes. The most common gene related to this condition is TGM1. Other genes include NIPAL4, ALOX12B, and CYP4F22. These genes provide the instructions to make enzymes and proteins. These enzymes and proteins are important for normal development, function, and shedding of skin cells. There is also evidence that more genes are related to LI. The severity of the condition cannot always be determined based on genetic testing results.
The harmful changes that cause LI are recessively inherited. Recessive genetic disorders occur when an individual inherits a non-working gene from each parent. If an individual receives one working gene and one non-working gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the non-working gene and therefore have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier, like the parents, is 50% with each pregnancy. The chance for a child to receive working genes from both parents is 25%. The risk is the same for males and females.