
 reactive perforating collagenosis is a rare perforating disorder.it is characterised by collagen bundles perforating the epidermis . 
 
reactive perforating collagenosis ( rpc ) is a rare form of transepidermal elimination ( tee ) disorder in which there is extrusion of altered collagen from the epidermis .
rpc can exist in two forms ; the commoner acquired form and the rare familial form . in the familial form ,
the lesions manifest in early childhood is not associated with pruritus and usually spontaneously resolves .
we herein report a rare case of rpc in a young child with similar complaints in sibling .
a 4 year old boy presented with complaints of multiple , recurrent , dark coloured raised lesions on face , elbows and outer aspect of both legs of 2 years duration .
the lesions would start as skin coloured papules which later developed dark central material . some of the lesions would heal on its own in about a month leaving behind residual hyperpigmentation .
patient 's mother complained that she had noticed new lesions occurring at sites of trauma .
there was history of similar complaints in his elder brother who was staying with his grandparents .
dermatological examination revealed multiple , discrete , symmetrical , hyperpigmented , hyperkeratotic papules distributed over face , both elbows and lateral aspect of both legs [ figure 1 ] .
hyperkeratotic papules with central plugging over elbows and evidence of koebnerisation similar lesions on lower limbs routine lab investigations were normal .
epidermis showed a hyperkeratotic crater filled with keratin , few polymorphonuclear leucocytes and occasional acellular basophilic fibrous strands .
the adjacent papillary dermis showed vertically oriented collagen bundles perforating the epidermis [ figure 3 ] .
the perforating collagen bundles were better delineated on van gieson stain [ figure 4 ] . based on clinical and histopathological features ,
the lesions showed some flattening with therapy but the patient continued to get new lesions at sites of minor trauma .
histopathology of skin lesions revealing epidermal parakeratosis and perforating bundles of collagen ( h and e , 40 ) perforating collagen bundles evident in van gieson stain ( van gieson stain , 40 )
. there are four different types of perforating disorders and all are characterized by transepidermal elimination of altered dermal substances .
they are kyrle 's disease , perforating folliculitis , elastosis perforans serpiginosa and reactive perforating collagenosis .
the inherited form of rpc is associated with a positive family history in about two thirds of patients .
consanguinity in parents is present in some cases with an autosomal recessive mode of inheritance , though dominant types have also been mentioned .
there is a slight male preponderance with siblings being affected as in our case . in the acquired variant ,
the lesions manifest after the age of eighteen years and are usually associated with itching .
it is also associated with hypothyroidism , hyperparathyroidism , liver disorders , hodgkin 's disease , neurodermatitis , hiv and iga nephropathy .
the morphology of lesions is similar in both the entities and consists of umbilicated papules and nodules that can be skin coloured , erythematous or hyperpigmented and characteristically have a central keratotic plug .
koebnerisation is commonly seen as in our patient . in genetically predisposed individuals , trauma results in altered collagen and
scratching induces lesions and common sites of involvement are the accessible and trauma prone sites , as seen in our patient also .
research has shown that in most cases no abnormality exists in the ultrastructure of the extruded collagen , but histochemical changes may be present .
histologically , early lesions show variable acanthosis and accumulation of collagen , which is basophilic in dermal papillae .
mature lesions show characteristic features of rpc where there is plug of parakeratotic material , basophilic debris and degenerated collagen lying within cup - shaped depressions in epidermis . as the condition resolves
the important treatment options are topical retinoids , topical corticosteroids , intralesional steroids , psoralen ultra violet - a , narrow band uv - b ( puva , nbuvb ) and allopurinol .
the familial form can also be associated with pruritus and may not spontaneously resolve as in our patient , which is not reported before . 

reactive perforating collagenosis can be rarely familial.the familial form can also be associated with pruritus and may not spontaneously resolve as in our patient . 
 
the familial form can also be associated with pruritus and may not spontaneously resolve as in our patient .
 a 4 year old boy presented with history of itchy raised lesions on body of 2 years duration . though parental consanguinity was not present , his elder brother had similar complaints . 
 dermatological examination revealed multiple hyperpigmented papules with a central keratotic plug distributed mainly over face and extensors of upper and lower extremities . 
 koebnerisation was present . 
 skin biopsy revealed perforating collagen bundles in the upper dermis and epidermis which was confirmed by van gieson staining . 
 patient was being treated with topical retinoids and intralesional corticosteroids with minimal relief . 
Introduction
Case Report
Discussion