a 19-year - old , single , unemployed , caucasian female ( skin type iii ) presented with multiple facial lesions .
she had been suffering from multiple pigmented annular papules and plaques on her face for 7 years .
she had been a normal , healthy , full - term baby and had normal physical milestones of development as a child .
she appeared to be immunocompetent with no history of recurrent infections or any other skin lesions .
her parents and siblings ( 3 brothers and 2 sisters ) were all normal and healthy .
her medical history was unremarkable with no other obvious complaints , and she was not overexposed to sunlight as she spent most of her time indoors . upon examination , the central part of the face , i.e. the malar area and nose including the ala nasi , showed scattered annular papules and plaques of different sizes ranging from 0.3 to 2 cm .
the lesions were asymptomatic and symmetrically distributed on both sides of the face ( figs . 1 , 2 ) .
the diagnosis was confirmed as dsap , with a classic and very illustrative pathological picture ( figs .
all physical modalities were excluded to avoid the possibility of side effects like scarring and disfigurement , as the lesions were located in the central part of the face and involved the skin overlying the nasal cartilage .
we first prescribed a topical retinoic acid 0.1% cream that has keratolytic and antineoplastic effects , and it was assumed that this might rectify the faulty clonal epidermopoiesis .
six months later , the patient presented again and the picture was almost unchanged except for a few small new lesions in the malar area and on the nose .
we decided to give her imiquimod 5% cream to be used once a day ( 3 times per week ) for 24 weeks .
side effects like erythema , crustations and pruritus were experienced and were controlled by topical emollient cream ; we avoided corticosteroids and calcineurin inhibitors because they can counter the effects of imiquimod . on completion of the therapy ,
central scarring and the scars across the nose improved in their color , thickness and texture , constituting an added benefit of imiquimod in this indication .
porokeratosis is inherited as an autosomal dominant trait ; however , sporadic cases are also known to occur . chernosky and freeman   first described dsap in 1967 in a texas population .
dsap is the most common of the clinical variants and may account for almost half of all cases in the usa , while in singapore it is second to the mibelli type in frequency ( 18 and 56% , respectively ) .
the incidence in females is double that of males , unlike the classic mibelli type .
dsap is characterized by multiple lesions that are superficial , relatively smaller than the mibelli type , slightly pigmented , annular , keratotic and with a central atrophic area .
it mainly affects areas exposed to sunlight ; however , paradoxically , the limbs are more affected than the face .
other regions such as the extensor surfaces of the extremities constitute the majority of reported cases , with cases of lesions appearing exclusively on the face being probably less frequent .
, dsap does not appear to have more risk of malignant change than other types .
it can sometimes coexist with other forms of porokeratosis ( mibelli type , linear porokeratosis , porokeratosis palmaris et plantaris disseminata and punctate porokeratosis ) .
there is good evidence that ultraviolet light can precipitate the development of new lesions or exacerbate pre - existing lesions .
our patient was minimally exposed to the sun and she spent most of her time indoors .
the exact pathogenesis of porokeratosis is not clear ; however , it has been assumed that a focal clonal expansion of abnormal cells gives rise to the shape of the coronoid lamella .
the coexistence of different variants in one patient or in several members of an affected family indicates different phenotypic expressions of a common genetic entity which could possibly be explained by a simultaneous expression of closely linked genes .
genetic studies have mapped the loci responsible for dsap to chromosomes 12q , 15q and 18q .
several mutations have been identified in the ssh1 gene on chromosome 12 , which encodes a phosphatase that plays a pivotal role in actin dynamics [ 10 , 11 ] . in a genome - wide scanning and linkage analysis performed on six generations of a chinese family with dsap ,
two missense mutations in ssh1 and arpc3 were found , which are involved in the actin cytoskeleton pathway and interact with adherent junctions in the epidermal cells .
this finding suggested that cytoskeleton disorganization in epidermal cells was likely associated with the pathogenesis of dsap . in a recent study on four chinese families , in 33% of the patients ,
three mutations were found in the mevalonate kinase ( mvk ) gene which plays a role in lipid metabolism .
psoriasis and phototherapy ( uva , bb - uvb and nb - uvb ) have been associated with porokeratosis .
dsap has also been associated with immune suppression , hiv infection , diabetes mellitus , liver cirrhosis , acute pancreatitis , crohn 's disease , solid malignancy , the administration of immunomodulating drugs used to treat autoimmune diseases and following the transplantation of organs ( particularly in kidney transplant patients ) [ 14 , 15 ] .
therapies such as cryotherapy , photodynamic therapy , erbium yag and co2 lasers or the application of topical 3% diclofenac gel or 5-fluorouracil cream are usually partially successful , but with inconsistent results .
this therapy treated the plaques effectively , there were no more keratotic elevations or furrows , and even the central scars showed an improvement in color and texture .
biologically , imiquimod is also antineoplastic and is used to treat nonmelanoma skin cancers ; this is a major added advantage because dsap may , in rare instances , be complicated by squamous cell carcinoma .
further studies are required to confirm whether imiquimod should have a place in the management of dsap .
the mechanism of action of imiquimod in the treatment of dsap is not yet clear : it may suppress or switch off the abnormal mutant genes through its immunological effects on both adaptive and innate immunity . in conclusion
, we presented a case of facial sporadic dsap , which was treated by application of imiquimod 5% cream in conjunction with regular sunscreens .
follow - up of this case is important to rule out the possibility of malignant transformation .
 porokeratoses are a group of hereditary or acquired disorders characterized by annular lesions with an atrophic center and a prominent peripheral ridge . 
 pathologically , porokeratosis is characterized by the presence of abnormal clones of keratinocytes that form a column of parakeratotic cells , called the cornoid lamella . 
 fifteen percent of patients of disseminated superficial actinic porokeratosis ( dsap ) have facial lesions ; other regions like the extensor surface of extremities constitute the majority of reported cases . exclusively facial lesions are probably less frequent . 
 rarely , actinic porokeratosis is confined to the nose only . 
 of reported porokeratosis cases , 7.5% have revealed a malignancy arising within the lesion . 
 we present a case of facial sporadic dsap that was treated with imiquimod 5% cream in conjunction with a regular sunscreen . 
 follow - up of this case is important to rule out the possibility of malignant transformation of the lesions . 