Pityriasis rosea in a patient with retrovirus infection: a reply

We read with interest the paper from Neneman et al. [1] about a case of pityriasis rosea (PR) in a patient with retrovirus infection and would like to make some comments. At the physical examination of their patient, the authors did not observe the mucous membranes to detect possible oropharyngeal lesions associated with PR. Indeed, although they stated that in PR “no eruptions are observed on the mucous membranes”, studies have shown that they may be observed in both Caucasian and dark skinned people [2]. Furthermore, we have recently reported that among 527 Caucasian patients with PR who between 2003 and 2016 attended the Dermatology Clinic of Genoa University, painless oropharyngeal lesions (enanthems) were observed in 149 (28%) cases. The most frequent lesions had petechial and maculo-papular patterns [3]. Interestingly, in our series, these enanthems were frequently associated with forms of PR different from the classic one: persistent [4], relapsing [5], pediatric PR [6] and PR during pregnancy [4, 7].
As regards the laboratory investigations, despite large amounts of evidence showing that PR is associated with the systemic endogenous reactivation of human herpesvirus (HHV)-6 and 7 [2], the authors did not perform serology for HHV-6/7 in their patient nor measure the HHV-6/7 DNA load in plasma by quantitative real-time polymerase chain reaction (PCR), the latter considered as a marker of active viral infection [8].
Regarding the etiology of PR, the authors stated that it is unclear [1]. However, a large number of studies have shown a causal role for HHV-6 and HHV-7 systemic endogenous reactivation in the pathogenesis of PR. In fact, HHV-6 and HHV-7 DNA were found in plasma and skin lesions of PR patients by real-time PCR and HHV-6 mRNA expression and specific antigens were found by immunohistochemistry in their skin lesions. Moreover, herpesvirus virions in various stages of morphogenesis were detected by electron microscopy in skin lesions and in the supernatant of co-cultured peripheral blood mononuclear cells (PBMCs) from PR patients [2]. The primary infection by HHV-6 and/or HHV-7 usually occurs in early childhood and may be asymptomatic, or may cause exanthema subitum (roseola infantum) or a febrile illness without any rash rarely accompanied by convulsions [2]. Afterwards they establish a long-life latent infections in different cells and organs, including monocytes, bone-marrow progenitors cells and salivary glands. The mechanisms...


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