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 .