Ichthyoses lacked the epidermal differentiation and tight junction alterations of patients with AD (loricrin, filaggrin, and claudin 1) but showed characteristic alterations in lipid metabolism genes (ELOVL fatty acid elongase 3 and galanin), with parallel reductions in extracellular lipids and corneocyte compaction in all ichthyoses except epidermolytic ichthyosis, suggesting phenotypic variations.
The lack of filaggrin is associated with various cutaneous (<i>e.g. ichthyosis vulgaris</i>, allergic contact dermatitis) and non-cutaneous (<i>e.g.</i> diabetes, inflammatory conditions of the gastrointestinal tract) diseases and may be a result of genetic, immunological factors combined with environmental factors.
This mixed phenotype suggests the need for a better understanding of the possible role of filaggrin loss and AP1 transcription factor deficiency in ichthyoses and collodion membrane formation.
Furthermore, our study strengthens the hypothesis that filaggrin defects can synergize with an STS deficiency to exacerbate the ichthyosis phenotype in an ethnically diverse population.
The study was made up of three groups including 9 Ichthyosis vulgaris (IV) patients, 50 AD patients and 55 normal controls: the ichthyosis group was incorporated due to the reported association between the FLG mutation and IV.
This is the second reported case of the modifying effects of FLG null alleles on XLI and strengthens the hypothesis that filaggrin defects can synergize with STS deficiency to exacerbate the ichthyosis phenotype.