porokeratoses are a group of cutaneous entities of unknown etiology , characterized by disordered epidermal keratinization and , at histological examination , by the presence of coronoid lamella , a column of parakeratotic cells extending through the stratum corneum
. disseminated superficial porokeratosis ( dsp ) is a distinct form of porokeratosis that , clinically , is characterized by numerous , small , superficial keratotic papules with verrucoid aspects , an atrophic center and peripheral keratotic border .
only 7 cases of this association have been described in the literature ( table 1 ) .
we report a eighth case of this type and an atypical immunohistochemical method used to characterize the amyloid substance .
a 76-year - old woman was referred to our department in june 1999 . she reported a 20 years history of an erythematous and squamo - papular eruption located on the extremities , without itching or pain .
the patient had noted a progressive extension of these lesions in the last year and an exacerbation of the lesions during the summer . upon physical examination ,
numerous papules with a size of less than 15 mm , an atrophic center and hyperkeratotic borders were distributed on the neck , chest and extremities .
palms , soles , mucous membranes and nails were spared , and the patient denied any family history of similar skin lesions .
we examined a skin biopsy that revealed atrophy of the epidermis with hyperorthokeratosis and presence of homogeneous and compact cornoid lamella of keratin , typically oriented sideways with respect to the epidermal tissue ( fig .
1 a ) . the superficial dermis showed a slight chronic inflammatory infiltrate with vascular ectasia and edema .
moreover , in the papillary dermis a compact deposit of a cellular eosinophilic material suspicious for amyloid was observed ( fig .
1b ) . to demonstrate the epithelial origin of the amyloid , we performed two immunohistochemical stainings by using specific moabs to pan - cytokeratin ae1-ae3 .
interestingly , there was a striking difference between the two results : in fact , the acellular deposits , mentioned above , were negative for ckae1-ae3 , whereas a strong immunoreactivity was demonstrated for ck5 , supporting a specific origin of the amyloid substance from the basal cell layer of the epidermis ( fig .
in 1937 , andrews first described dsp and introduced this term to indicate a clinical variant of mibelli 's porokeratosis . later , chernoski and freeman proposed a possible actinic etiology of this dermatosis and coined the term disseminated superficial 
nowadays , this term is generally accepted in european dermatological literature , and this definition is based on clinical and histological findings .
dermatological manifestations are typically confined to sun exposed areas , with actinic induction and exacerbations . in the literature , two types of localized cutaneous amyloidosis ( lca ) are described : primary lca ( macular amyloidosis and lichen amyloidosis ) , which is not associated with other dermatoses or systemic involvement , and secondary lca , which is associated with inflammatory , hamartomatous or neoplastic skin disorders . the mechanism by which dsp induces dermal amyloid deposits is not clear , but piamphongstant et al . first suggested that this process can derive from degenerated epidermal keratinocytes .
we hypothesize that a mutant keratinocyte clone is responsible for induction of porokeratotic lesions , because these necrotic epidermal keratinocytes ( colloid bodies ) might be transformed into amyloid by dermal macrophages and fibroblasts .
immunohistochemical staining has shown an overexpression of p53 protein in porokeratotic lesions ; this is a tumor suppressor protein , an important gatekeeper and effector of the cell cycle .
mutations of the p53 gene in all forms of porokeratosis , also in dsap , create a permissive state of uncoordinated cell cycling , and predispose cells to death . in our case , the lack of systemic involvement led to our hypothesis of a secondary dermal deposition of amyloid proteins and the existence of a close relationship between these two processes .
this hypothesis was confirmed by positive staining with congo red and immunohistochemical staining with the anticytokeratin moabs strongly positive for ck5 , just below the epidermal porokeratotic zone in close proximity to the cornoid lamella .
this cytokeratin is , in fact , strongly represented in the basal cell layer and these results indicate that the dermal deposits were amyloid originating from the epidermis ( type ii keratin ) .
nowadays , more studies are necessary to clarify the exact mechanism that leads to secondary deposition of dermal amyloid in porokeratotic disease and the frequency of this association .
we also suggest utilization of moabs for ck5 as a first - line target in these conditions , encouraged by the immediate and strong positivity of this protein in immunohistochemical studies , whereas pan - cytokeratin at first produced negative results .
 only 6 cases with an association of disseminated superficial porokeratosis with dermal amyloid deposits are reported in the literature . 
 we present the case of a 76-year - old woman who presented with a disseminated superficial porokeratosis . 
 histological examination revealed amyloid deposits in the upper dermis , which were typed with routine he stains , congo red stains and anticytokeratin antibodies ( ae1-ae3 and ck5 ) . 
 positive staining with congo red and , moreover , with ck5 ( a cytokeratin strongly represented in the basal cell layer of the epidermis ) indicates an epidermal origin of this protein . 