FLG and inherited ichthyosis: These filaggrin degradation products play a role in the water-holding capacity and hydration of the stratum corneum and are crucial for epidermal barrier homeostasis [39]. A filaggrin deficiency can disrupt the stratum corneum's moisture-retaining capacity and hydration by disrupting corneocyte structure and diminishing the production of NMF. Many skin barrier disorders, such as atopic dermatitis, ichthyosis vulgaris, and xerosis cutis, have been associated with filaggrin deficiency.