Filaggrin gene mutations and the distribution of filaggrin in oral mucosa of patients with oral lichen planus and healthy controls

Ichthyosiform Lichen Planus Pigmentosus in a 19-Year-Old Male Patient: Case Report

Lichen planus pigmentosus (LPP) is a condition characterized by persistent and asymptomatic brownish-black-to-blue or purple-gray pigmentation, predominantly in the face and sun-exposed areas, commonly in dark-skinned individuals. Several clinical variants of LPP have been reported. However, the ichthyosiform type of LPP has not been reported. We present a 19-year-old male patient who presented with a 7-year history of asymptomatic grayish macules; patches with fine scales on the face, trunk, and upper extremities; and grayish plaques with thick "ichthyosiform" scales on the lower extremities. The diagnosis of LPP was proven by histopathological findings on both the macular and ichthyosiform plaques. Cluster differentiation (CD) 68 stain highlights the same density of pigment-laden macrophages in both the gray macule and the ichthyosiform plaque. The cause of LPP is unknown. Transcription factor anomalies may play a role in increased keratinization of lichen planus lesions. It can be assumed that the mechanism of the altered distribution of keratinization may occur on the ichthyosiform lesions in this patient. The terminology "ichthyosiform lichen planus pigmentosus" is hereby proposed to be added to the clinical variants of LPP.

Filaggrin gene mutations with special reference to atopic dermatitis

Purpose of review

Mutations in the Filaggrin gene can cause absent or reduced filaggrin protein, leading to impaired keratinization and skin barrier defect, which produce characteristic phenotypes. In this short review, we report current evidence on the topic with special reference to atopic dermatitis, suggest future directions, and discuss therapeutic implications.

Recent findings

Numerous candidate gene association studies, genome-wide association studies, studies on copy number variations and most recently, sequencing studies, have confirmed the robust association of mutations in the Filaggrin gene with atopic dermatitis, and have also linked these mutations with several other disorders.

Summary

Filaggrin gene defects remain the strongest identified genetic risk factors for atopic dermatitis. Taken in conjunction with other genes found to be associated with this condition, genetic screening and identification of individuals at risk for atopic dermatitis could lead to personalized therapy. Manipulation of genetic regulatory elements to increase the amount of filaggrin protein in deficient individuals is an attractive treatment option for the future.

Peptidylarginine deiminase is involved in maintaining the cornified oral mucosa of rats

BACKGROUND AND OBJECTIVE

Epithelial cells derived from different regions exhibit marked differences in their differentiation capacity, allowing them to provide a suitable protective barrier. We aimed to clarify the role of peptidylarginine deiminase (PAD) in modifying the key epidermal proteins filaggrin (FLG) and keratin 1 (K1) during stratification of the rat palate and buccal mucosa.

MATERIAL AND METHODS

We performed immunofluorescence, immunoblotting, PAD activity assays and 2-dimensional electrophoresis, and developed an organotypic culture model.

RESULTS

PAD1 expression was highest in the palate, whereas PAD2, PAD3 and PAD4 expression was highest in the skin, suggesting the tissue-specific expression of PAD isozymes that leads to differences in calcium dependency. Immunoblotting showed that the FLG monomer, as well as its degradation products and precursor (proFLG), were most abundantly expressed in the skin but had low expression in the palate, whereas only faint proFLG expression was detected in the buccal mucosa. FLG and K1 were colocalized with PAD1 and were likely to be citrullinated in the cornified layers of the skin; this colocalization was not detected on the palatal surface, and dot-like presence of proFLG that might be citrullinated and that of PAD1 were found in the granules of the palate. Organotypic models derived from the rat palate revealed that PAD inhibition reduced the breakdown of FLG, increased its association with K1 together with epithelial compaction, and decreased permeability in a dye permeability assay. Conversely, PAD stimulation had the opposite effects.

CONCLUSION

Citrullination is likely a protein modification that plays an important role in maintaining the structure and function of oral cornified mucosa in a way that is distinctly different from that of the skin.