porokeratosis are disorders of keratinization characterized histologically by a parakeratotic column , the cornoid lamella , and clinically by a distinct peripheral ridge . porokeratosis is characterized by annular plaques with an atrophic center and hyperkeratotic edges clinically , although it has a wide variety of clinical manifestations . the various morphological types recognized are : porokeratosis of mibelli ( pm ) disseminated superficial actinic porokeratosis ( dsap ) , porokeratosis palmaris et plantaris disseminata ( pppd ) and linear porokeratosis ( lp ) . the lesions are inherited as an autosomal dominant condition , but frequently sporadic cases are seen . exact pathogenesis is not known but an abnormal early keratinocyte apoptosis accompanied by dysregulation of terminal differentiation ( keratinization ) has been suggested for pathogenesis of cornoid lamella . a 34-year old woman presented with asymptomatic lesion on her nose . on physical examination , there was a one cm plaque , which had hyperkeratotic ridge and depressed center on the right site of the nose [ figure 1 ] . no involvement of the trunk , extremities or mucous membranes was observed , and the patient was otherwise healthy with no developmental problems . histopathological examination of a biopsy taken from the edge of the nasal lesion revealed cornoid lamellae confined exclusively to the follicle and a few area overlying an absent granular layer [ figure 2 ] . 1 cm plaque , which had hyperkeratotic ridge and depressed center on the right site of the nose cornoid lamellae confined exclusively to the follicle and a few area overlying an absent granular layer two patient were reported with facial porokeratosis by nabai et al . first in 1979 . there have been a few reports of exclusive facial involvement in porokeratosis , with skin lesions mostly over or near the nose . follicular involvement , identified by follicular localization of cornoid lamellae , is uncommon and described only in association with other subtypes such as dsap , pm , and exclusive follicular cornoid lamella in follicular porokeratosis . in 1893 , mibelli named porokeratosis based on the assumption that the columns of parakeratosis emerge from the ostia of eccrine ducts . in the same year , raspighi emphasized the plugging of the follicular infundibulum and acrosyringium of porokeratosis . there were nine well documented reports follicular porokeratosis in the english literature [ table 1 ] . four of them were located on face and five of them located at extremities and the body . on histopathological examination , follicular cornoid lamellae were noticed first by de almeida et al . in 2007 . of these , 33 lesions from 32 patients were related to follicular infundibulums including consecutive sections , and there was no correlation between clinical subtype and the association of cornoid lamellae with cutaneous appendages . presentation exclusively on the face seems to have no correlation with follicular involvement of the cornoid lamellae . pongpudpunth et al . published a case that had clinically characteristic dsap located on the extremities and body , which were characterized histopathologically by follicular involvement on histopathologic examination solar elastosis was not shown , whereas , wang at al showed solar elastosis histophatologically , different from our case . while follicular porokeratosis is accepted as a distinct histopathologic entity in some publications , but it did nt enter clinical classification . follicular porokeratosis cases reported previously in the literature , and our case in conclusion , porokeratosis should be considered when atrophic skin lesion is seen on nose , although a rare condition . histophatologically , follicular porokeratosis is different from classic porokeratosis in terms of placement of parakeratotic columns in follicular infundibulum . pathologists having knowledge of this new histopathologic entity will help dermatologists in identifying new cases of follicular porokeratosis .
porokeratosis are disorders of keratinization , characterized histologically by a parakeratotic column , the cornoid lamellae , and clinically by a distinct peripheral ridge . 
 porokeratosis usually occurs on the trunk or extremities , and facial lesions are rare . 
 follicular involvement , identified by follicular localization of cornoid lamellae , is uncommon and described only in association with disseminated superficial actinic porokeratosis ( dsap ) and porokeratosis mibelli ( pm ) . 
 a 34-year- old woman is presented with asymptomatic 1 cm plaque lesion with hyperkeratotic ridge and depressed center on her nose since three years . 
 histopathological examination of a biopsy revealed cornoid lamellae confined exclusively to the follicle .