Human polyomavirus 6/7-associated pruritic and dyskeratotic dermatosis

Older adults, people with chronic immunosuppression.

HPyV6 and HPyV7 belong to the Polyomaviridae family. Both viruses can be part of the cutaneous virome of clinically healthy individuals. Therefore, the mere detection of their DNA in a skin biopsy does not prove the presence of a disease-causing infection.

Under conditions of immunosuppression (and in old age?), there appears to be increased viral replication or expression of viral proteins in epidermal keratinocytes. The associated changes in epidermal differentiation are thought to underlie dyskeratotic dermatosis.

Mainly the trunk, back, and extremities; occasionally also the face, armpits, and palms.

The clinical presentation consists of generalized, symmetrically distributed, sometimes lichenoid or hyperkeratotic, grayish-brown to livid-brown, intensely itchy, and scaling macules, papules, and plaques.

Characteristic dyskeratoses and parakeratoses, referred to as“peacock plumage”(Note: this phenomenon is unlikely to have any particular diagnostic significance!).

In these cases, there are (virus-induced)

• irregularly arranged, vertically layered columns of parakeratosis.
• Eosinophilic, dyskeratotic keratinocytes in various layers of the epidermis.
• Enlarged keratinocytes with viral inclusion bodies or cytopathic changes.
• Occasionally, vacuolar basal cell changes and a low-grade perivascular lymphocytic infiltrate.

The diagnosis is based on a combination of clinical findings, characteristic histopathology, and virological evidence.

Key factors include a high viral load in the affected skin as determined by quantitative PCR, immunohistochemical detection of viral T-antigens or capsid proteins in altered keratinocytes, and, if applicable, the identification of intact virions by electron microscopy. A positive PCR result alone is not sufficient due to the possibility of asymptomatic viral persistence

Due to the rarity of the disease, there is no standardized treatment supported by controlled studies.

The primary focus, as clinically feasible, is on reducing immunosuppression as well as symptomatic, keratolytic, and skin-care treatments.

Case reports describe improvements with topical tretinoin or systemic acitretin.

No specifically effective antiviral therapy has been established.

HPyV6 and HPyV7 are of interest in the context of chronic pruritus because they represent a rare, virologically defined cause of persistent itchy skin conditions.

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