Koebner Phenomenon in a Young Boy With Henoch-Schönlein Purpura
A 5-year-old boy presented with complaints of skin rash, pain in multiple joints, and pain in the abdomen. On examination, he had palpable purpuric rash involving the lower limbs (Fig. A), upper limbs, ear lobules, and face and arthritis of the bilateral ankle, wrist, and elbow joints. He was also noted to have linear band of palpable purpuric rash in the arms and legs (Koebner phenomenon) (Fig. B), which developed at the site where a thread was tied because of religious reasons. Histopathologic examination of skin biopsy revealed leukocytoclastic vasculitis with immunoglobulin A deposits on immunofluorescence. The diagnosis of Henoch-Schönlein purpura (HSP) was proffered, and oral prednisolone was prescribed for 7 days, which was gradually tapered over next 4 weeks.
Koebner phenomenon is described as an isomorphic skin response, that is, the development of similar skin lesions at the site of pressure. Skin diseases that are well known to exhibit Koebner phenomenon include psoriasis, lichen planus, and vitiligo; however, it has rarely been reported in association with vasculitis. Henoch-Schönlein purpura is a small vessel vasculitis and is more common in children. Koebner phenomenon has been described in few adult HSP cases1,2 and recently in 2 pediatric HSP patients.3 The pathogenesis of Koebner phenomenon associated with vasculitis is believed to be due to aggregation of immune complexes at the site of pressure or trauma.