Psoriasis Over Healed Herpes Zoster: Wolf's Isotopic Response.

Sir,

The term “Wolf's isotopic response” refers to the occurrence of a new unrelated dermatosis at the same location as a previously healed dermatosis.[1] The most common preceding dermatosis is herpes zoster. Many dermatological entities can develop at the site of healed herpes zoster such as granulomatous processes, papulosquamous diseases, lymphomas, pseudolymphomas, primary skin tumors, and metastatic deposits.[2] We hereby describe a patient who developed psoriatic lesions on the site of previous herpes zoster.

A 35-year-old female who had suffered from herpes zoster 6 months back consulted for a rash that had been present for the preceding 2 weeks, over the healed lesions of herpes zoster, corresponding to the left thoracic dermatomes T8–T10. To start with, there a few scaly, red, and elevated lesions over the healed areas of herpes zoster, which increased in number and dimensions to attain the present status. Cutaneous examination showed multiple erythematous scaly papules coalescing to form plaques distributed over the left T8–T10 dermatomes [Figure 1]. Besides, there were a few hypopigmented patches in the vicinity of the psoriatic lesions, which represented postinflammatory hypopigmentation marks following herpes zoster. Skin biopsy was done from an erythematous papule, and the histopathology showed hyperkeratosis, parakeratosis, acanthosis, neutrophilic microabscesses, edematous papillary dermis, and dilated blood vessels [Figure 2]. Dermoscopy showed regular arrangement of dotted vessels and white scales [Figure 3]. Based on clinicopathological correlation and dermoscopy, the diagnosis was confirmed as psoriasis. Taking into consideration the preceding history of herpes zoster, our case was a classical example of Wolf's isotopic response wherein psoriasis developed at the sites of healed herpes zoster.

Figure 1

Clinical photograph showing erythematous scaly plaques present over the site of healed herpes zoster

Figure 2

Histopathology shows hyperkeratosis, parakeratosis, acanthosis, neutrophilic microabscess, suprapapillary thinning, and dilatation of dermal vessels (H and E, ×10)

Figure 3

Dermoscopy shows white scales (black arrow) and regular arrangement of dotted vessels (blue circle) (Heine Delta 20 Polarized)

It was the first time in 1955 when Wyburn-Mason described the occurrence of a new unrelated disease at the site of a previously healed disease.[3] This was coined as “isoloci response” by Wolf in 1985.[4] Later on, it was renamed as “isotopic response” followed by “Wolf's isotopic response.”[15] The dermatoses which are known to present in the site of previously healed disease include granulomatous reactions, malignant tumors, leukemic infiltrates, dermatoses secondary to immunologic dysfunction, infections, comedogenic reactions, and other miscellaneous conditions.[6]

The etiopathogenesis behind this response remains inconclusive. Various hypotheses have been put forward. However, the neural hypothesis is the most accepted one. During herpes zoster, varicella zoster virus causes destruction of the A-delta and C nerve fibers. Besides, neurohumoral factors stimulate the development of the second dermatosis by releasing substance P, bradykinin, serotonin, vasoactive intestinal peptide, calcitonin gene-related peptide, and α-melanocyte-stimulating hormone. These neuropeptides initiate the immunological cascade of the pathogenesis of the second disease. In addition to this, neurohumoral factors lead to unregulated activation of the immune system which contributes to the isotopic response. Allegue et al. proposed the role of tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of this isotopic response. TNF-alpha is known to possess antiviral activity, and the levels are elevated in herpes zoster. Besides, TNF-alpha is also elevated in psoriatic skin lesions. Therefore, it can be hypothesized that increased levels of TNF-alpha during the course of herpes zoster could serve as a triggering factor for the development of psoriasis over the healed sites.[6]

Numerous dermatoses have been reported to occur as a part of Wolf's isotopic response. However, psoriasis is a rarely reported condition. Allegue et al. documented a case of psoriasis developing over T6 and T7 dermatomes in a known case of healed herpes zoster.[7] Our case adds to the list of documented examples of Wolf's isotopic response over the sites of healed herpes zoster. The second dermatosis being psoriasis adds to the uniqueness of the present report.

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Conflicts of interest

There are no conflicts of interest.