First described in 1877 as the appearance of psoriatic lesions in the uninvolved skin of psoriatic patients as a consequence of trauma, the Koebner phenomenon has since been described in numerous diseases. Other authors have tried to implicate either infections or parasitic causes as the pathogenesis of this phenomenon. Subsequent research by many authors have contributed to our poor understanding of this reaction in the hope of understanding the pathogensis of psoriasis. We present a review of the literature covering the following topics as they relate to the Koebner phenomenon: diseases that koebnerize and their possible causes, predisposing and provoking factors, type, site, depth and degree of trauma, the all or none phenomenon, time lag, site preference, medications, inhibition of koebnerization and reverse koebnerization.

Background: Exaggerated reaction to insect bites, mainly to mosquitoes, is infrequently described in patients with chronic lymphocytic leukemia. Skin lesions usually appear months to years after the diagnosis of leukemia and are unrelated to laboratory findings, disease course, or therapy.Observations: We describe 8 patients with various hematologic disorders (chronic lymphocytic leukemia, acute lymphoblastic leukemia, acute monocytic leukemia, mantle-cell lymphoma, large-cell lymphoma, and myelofibrosis) who developed insect bite-like reaction. Although the clinical picture and the histological characteristics of the lesions were typical for insect bites, none of the patients actually had a history, course, or response to treatment suggestive of arthropod assaults. In 2 patients, the eruption preceded the diagnosis of the ma-lignant neoplasm. The rash persisted for months to years and was resistant to therapies other than systemic corticosteroids. The 3 patients with chronic lymphocytic leukemia seemed to have a worse prognosis than expected for their disease. In 1, the polymerase chain reaction detected leukemic cells in the infiltrate.Conclusions: Insect bite-like reaction is an infrequent, disturbing, and difficult-to-treat nonspecific phenomenon in patients with hematologic malignant neoplasms. Since it may precede the hematologic disorder, oriented evaluation is warranted. We speculate that immunodeficiency plays a role in its pathogenesis; however, the exact pathogenesis and its prognostic implications await further studies.

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