FLG and ichthyosis vulgaris: The first suggestion of the involvement of filaggrin in barrier maintenance was reported by Sybert et al. (Sybert et al., 1985) where reduction of its expression was correlated with ichthyosis vulgaris (IV); follow-up studies confirmed reduction or loss of filaggrin expression with epidermal barrier dysfunction (Fleckman et al., 1987; Peña Penabad et al., 1998).