Lamellar ichthyosis

Lamellar ichthyosis is a condition that mainly affects the skin. Infants with this condition are typically born with a tight, clear sheath covering their skin called a collodion membrane. This membrane is usually shed during the first few weeks of life, but remaining effects include scaly skin and outward turning eyelids and lips. People with lamellar ichthyosis typically have large, dark, plate-like scales covering their skin. Affected individuals may also have hair loss (alopecia), a decreased ability to sweat (hypohidrosis), and a thickening of the skin on the palms of the hands and soles of the feet (keratoderma). Less frequently, affected individuals have reddened skin (erythema) and joint deformities (contractures). Infants with lamellar ichthyosis may develop infections, an excessive loss of fluids (dehydration), and respiratory problems.

Lamellar ichthyosis is estimated to affect 1 in 200,000 to 300,000 individuals in the United States. This condition is more common in Norway, where an estimated 1 in 90,000 individuals are affected.

Mutations in at least three genes can cause lamellar ichthyosis. These genes provide instructions for making proteins that are found in the outermost layer of the skin (the epidermis). The epidermis forms a protective barrier between the body and its surrounding environment. The skin abnormalities associated with lamellar ichthyosis disrupt this protective barrier, making it more difficult for affected infants to control water loss, regulate their body temperature, and fight infections.

Mutations in the TGM1 gene are responsible for approximately 90 percent of cases of lamellar ichthyosis. TGM1 gene mutations lead to impaired formation of a structure called the cornified cell envelope, which surrounds skin cells in the epidermis. This envelope gives skin its flexibility by retaining water and helps protect the body from infection.

Mutations in the other genes associated with this condition are found in only a small percentage of cases. In some people with lamellar ichthyosis, the cause of the disorder is unknown. Researchers have identified several chromosome regions that may contain genes associated with lamellar ichthyosis, although they have not been able to identify the specific genes.

Read more about the TGM1 gene.

See a list of genes associated with lamellar ichthyosis.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.