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Keywords:

  • apoptosis;
  • isomorphic reaction;
  • Köbner's phenomenon;
  • subacute cutaneous lupus erythematosus;
  • wasp sting

Lupus erythematosus (LE) is well known to be induced by several stimulating events such as exposure to sunlight, infectious and noninfectious inflammatory diseases including appendicitis (1), treatment with various drugs (e.g., procainamide, carbamacepine, chlorpromacine), and pregnancy. Surprisingly, Köbner's phenomenon has been only rarely described in patients with LE (2). Here we report on a female patient with subacute cutaneous lupus erythematosus (SCLE) caused by an insect sting. A 79-year-old Caucasian woman with a 2-year history of SCLE presented with a purple-red, scaly plaque of approximately 10 cm in diameter on the back of the right hand (Fig. 1). She told us that she had been stung by a wasp 2 months before and had initially developed an edematous swelling in the mentioned area. Wasp-sting köbnerization of the underlying SCLE was suspected. To exclude induction of the LE by contact sensitization to one or more allergens of applied creams, she was patch tested with the standard series of the International Contact Dermatitis Research Group (ICDRG), an ointment series, and the topical treatments used. We did not detect any contact sensitization. A skin biopsy (right hand) showed orthokeratosis covering a hydropic degenerated epidermis in which lymphocytes were visible, pigment incontinence, discrete extravasation of erythrocytes, colloid bodies, and splitting of the PAS-positive basement membrane. Total IgE was 110 kU/l, IgE against bee venom was 4.18 kU/l, and that against wasp venom was 10.0 kU/l. Because she did not suffer LE eruptions after other traumatic events such as nettle stings, it was suspected that an IgE-mediated allergic reaction had induced the SCLE skin lesions.

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Figure 1. Dorsal aspect of right hand 2 months after wasp sting shows erythematosquamous plaque and erythematous papules.

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Köbner's phenomenon, or isomorphic reaction, first described by Heinrich Köbner in 1876, is defined as the development of skin lesions in previously normal skin after traumatization by either internal or external influences. It is well known in patients with psoriasis and has been reported in several other skin diseases such as lichen planus, vitiligo, bullous pemphigoid, etc. (3). In patients with LE, it has been only rarely described (2). Contact dermatitis, scratching effects, pressure from sock tops, exposure to liquid or silica, tattoos, operation scars, striae cutis distensae, thermal injury, and other traumatic events have been reported to induce LE (2). Our case is the first report of a wasp sting inducing SCLE, and it is of special interest because, in contrast to the cases reported so far, LE exacerbation could be observed not only within the irritated skin area but also elsewhere on the skin far away from this site. It was suspected that it was not the mechanical sting but an IgE-mediated inflammatory reaction that had triggered LE. Because autoantibodies are uncommon in LE triggered by köbnerization (2), it is reasonable to assume that such patients may have increased susceptibility to minimal traumatic events and could react with increased apoptosis of epidermal cells. Apoptotic keratinocytes are a hallmark of LE skin lesions (4). Moreover, lupus antigens, normally hidden within cells, are present in small surface blebs of cells undergoing apoptosis. In summary, the presented case demonstrates that Köbner's phenomenon seems to be a relevant mechanism in the pathogenesis of LE. Therefore, patients with LE should be asked about external and/or internal triggering events.

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Footnotes
  1. First case of subacute cutaneous LE showing köbnerization after sting.