Expression of Filaggrin in the Ichthyosiform Dermatoses

Cha, Seung Hoon; Kim, Ju Seop; Won, Young Ho; Park, Seok Don

Abstract

BACKGROUND: Ichthyosis is the name of a group of disorders characterized by a generalized, persistent, non-inflammatory scaling disorder of the skin. Filaggrin is an intermediate filament associated protein which functions to aggregate keratin intermediate filaments in the stratum corneum of mamrnalian epidermis. It is synthesized as a large precursor protein, profilaggrin, that consists of multiple filaggrin units and is localized in keratohyalin granules(KHG). Some reports elucidated the pathogenetic role of filaggrin in ichthyosis, especially autosomal-dominant ichthyosis(ADI).
OBJECTIVE
We conducted an immunohistochemical study in order to observe the relationship between clinical phenotypes of various ichthyosiform dermatoses and the exprassion of filaggrin.
MATERIALS AND METHODS
Clinically and histopathologically proven ADI, lamellar exfoliation of the newborn, lamellar ichthyosis, epidermolytic hyperkeratosis, and acquired ichthyosis cases were included in this study. Using monoclonal mouse anti-human filaggrin antibodies, an immunohisto-chemical study was performed with formalin-fixed, parraffin-embedded involved skin tissues via the ABC technique.
RESULTS
Filaggrin was staind linearly or in a punctuate pattern along the granular cell layer of the normal epidermis. The expression of the filaggrin was decreased or partly absent in the skin tissue of ADI in accordance with the changes of KHGs. Similar immunoreactivities with filaggrin antibodies were noted in the skin of acquired ichthyosis. In lamellar exfoliation of the newborn, filaggrin was staineil from the stratum granulosum to the mid-layer of the stratum corneum with basket-weave byperkeratosis. Filaggrin was intensely and focally labelled in the normal acrosyringium of the lamellar ichthyosis from the granular layer to the mid horney layer. A decreased positive immunorcactivity was observed in the interfollicular stratum granulosum. A strong immunoreactivity was noted in the area with relatively normal KHGs of epidermolytic hyperker atosis, and a decreased l membranous staning pattern was observed in the layer with degenerated vacuolar KHGs.
CONCLUSION
It can be concluded that decreased expression of filaggin may play a causative role in the pathogenesis of ADI. However in lamellar exfoliation of the newborn, lamellar ichthyosis, epidermolytic hyperkeratosis, and acquired ichhtyosis, the altered expression of filaggrin must reflect the changes of KHGs in the stratum granulosum.