Dermatology Online Journal

Koebner's phenomenon in Henoch Schoenlein purpura and role of pressure in its causation
KC Nischal, Khopkar Uday, Bhor Urmila
Dermatology Onine Journal 13(2): 26

Department of Dermatology, Seth G.S. Medical College and K.E.M Hospital, Parel, Mumbai, Maharashtra, India.

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Henoch Schönlein purpura (HSP) is one of the commonest causes of small vessel vasculitis and often presents with only a purpuric rash. Inspite of its common occurrence, Koebner's phenomenon has been rarely reported in this condition [1]. We hereby report this case firstly to highlight the occurrence of Koebner's phenomenon in HSP and secondly the role of pressure in elicitation of this phenomenon.

A 42-year-old male presented with red rash over both legs since 2 days. The rash was preceded by low-grade fever and mild abdominal pain. However there was no history of sore throat or ingestion of any medication. Rash started as few red raised lesions around ankle and gradually increased in size and number to involve lower third of both thighs. Patient wore a pair of new socks which had tight elastic in its upper part. Following day, patient observed horizontal strips of red raised area at the site of pressure from socks elastic band. There was no history of hematuria or arthralgia.

On examination patient had multiple palpable purpuric papules and plaques on dorsum of feet and both legs extending onto the lower third of thighs. In addition to these typical lesions, the patient had bilateral, tender, horizontal bands of palpable purpura over proximal third of legs at the site corresponding to the elastic band of the new pair of socks worn by him [Fig. 1]. These discrete bands had coalesced to form broad edematous plaques in the medial aspect of both legs. As with the abdomen, there was no tenderness. Biopsy from the band like purpuric plaque revealed leukocytoclastic vasculitis [Fig. 2] consistent with the diagnosis of HSP.

Figure 1	Figure 2
Figure 1: multiple palpable purpuric papules and plaques both legs with horizontal bands of palpable purpura at the site corresponding to the elastic band of the socks. Figure 2: Biopsy from the palpable purpura revealing leukocytoclastic vasculitis.

Henoch Schönlein purpura is a common dermatosis affecting all age groups. Koebner's or isomorphic phenomenon is occurrence of clinically similar lesions on uninvolved skin along sites of trauma in patients with pre-existing dermatosis. Koebners' phenomenon has been reported in a variety of dermatoses [2]. However, to this date, there is only a single report in English literature of Koebner's occurring in this condition [1]. Because of the paucity of reports, Boyd and Nelder have classified HSP as a questionable isomorphic phenomenon [3].

The various causes for Koebner's phenomenon have been broadly classified as mechanical trauma, dermatoses, and therapy-induced. As observed in our patient, pressure from various mechanical factors such as socks and pressure sleeves have been purported to be a cause of isomorphic phenomenon [4, 5]. Contrary to these reports, Miller et al. have demonstrated inhibition of Koebner's phenomenon on application of pressure [6]. Unless the exact patho-mechanism is elucidated, this conflicting observation cannot be resolved with the existing hypothetical immunologic, vascular or neural pathogenetic theories [2].

Although with our observation we can neither add to the pathogenesis of Koebner's phenomenon nor resolve the conflict of reports with respect to implication of pressure in elicitation of this phenomenon, we can definitely benefit our patients with HSP. We can advise the patients with HSP not to wear any constricting bands or tight fitting clothes during the active phase of disease and thereby restrict the severity and progression of HSP.

References

1. Green ST, Natarajan S. The Koebner phenomenon in anaphylactoid purpura. Cutis.1986 Jul;38(1):56-7. PubMed

2. Thappa DM. The isomorphic phenomenon of Koebner. Indian J Dermatol Venereol Leprol 2004;70:187-189.

3. Boyd AS, Neldner KH. The isomorphic response of Koebner. Int J Dermatol. 1990;29:401-10. PubMed

4. Bernstein EF, Kantor GR. Treatment-resistant psoriasis due to a mastectomy sleeve: an extensive Koebner response. Cutis. 1992 Jul;50(1):65-7. PubMed

5. Ueki H. Kobner phenomenon in lupus erythematosus. Hautarzt 1994 Mar;45(3):154-60. PubMed

6. Miller RA, Griffiths WA. Pressure inhibition of the Koebner reaction by capillary occlusion. Acta Derm Venereol 1982;62(4):331-3. PubMed

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