Premature apoptosis of keratinocytes and the dysregulation of keratinization in porokeratosis.
BACKGROUND
Porokeratosis is a dyskeratotic disorder of the skin characterized by cornoid lamella with parakeratosis, hyperkeratosis and loss of granular layers. The pathogenesis of porokeratosis and the mechanism(s) of its abnormal keratinization are still unknown.


OBJECTIVE
To elucidate the mechanism(s) of abnormal keratinization that leads to the formation of cornoid lamellae in porokeratosis.


METHODS
Apoptosis of keratinocytes was assessed in the skin of seven patients by an in situ apoptosis assay based on the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) reaction. Patterns of loricrin and involucrin expression were examined by immunohistochemistry.


RESULTS
TUNEL-positive keratinocytes were observed in the epidermis underlying the cornoid lamella in all cases examined. Furthermore, loricrin expression was interrupted there, in contrast to involucrin, which was expressed diffusely in the lesional epidermis.


CONCLUSIONS
These results suggest that an abnormal early keratinocyte apoptosis accompanied by dysregulation of terminal differentiation of those cells may be involved in the pathogenesis of porokeratosis.
Department of Dermatology, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto 602-8566, Japan.
C-S
CS
Shen
K
K
Tabata
M
M
Matsuki
T
T
Goto
T
T
Yokochi
K
K
Yamanishi
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D002454:Cell Differentiation; D015536:Down-Regulation; D004817:Epidermis / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000473:pathology*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008875:Middle Aged; D017499:Porokeratosis / Q000378:metabolism / Q000473:pathology*; D011498:Protein Precursors / Q000378:metabolism
D008565:Membrane Proteins; D011498:Protein Precursors; C064554:loricrin; C032253:involucrin