Hereditary ichthyosis vulgaris is an autosomal dominant genetic disorder first evident in early childhood. It is the most common form of ichthyosis, accounting for more than 95% of ichthyosis cases and is the most common disorder of the skin caused by a single defect in a gene - filaggrin (FLG).
The filaggrin protein is responsible for the aggregation of keratin filaments on the outer layers of skin. The absence of this protein results in generalized, fine scaling of the skin that is often associated with atopic dermatitis. Phenotype severity is genetic, wherein heterozygous patients show a milder phenotype with reduced FLG, and ichthyosis vulgaris patients have homozygous or compound heterozygous FLG mutations typically lack FLG and exhibit a more severe scaling phenotype.
This disease is common in the United States, with a prevalence of approximately 1 case in 300 persons*. The gene defect that causes ichthyosis vulgaris is also the root cause of moderate to severe childhood eczema and some forms of asthma.
*Schwartz R. Hereditary and Acquired Ichthyosis Vulgaris. Medscape; http://emedicine.medscape.com/article/1112753-overview#a4; Updated July 19, 2017