Primary varicella is a self‐limited infection characterized by fever and a distinctive vesicular rash lasting about 5 days that is more intense on the trunk, face, and scalp than on the extremities. The vesicles initially contain clear fluid, rapidly pustulate, and subsequently scab. The lesions appear in crops so that on any one part of the body the rash can be in different stages of development. For example, primary varicella may present itself with a distinctive vesicular rash that is more intense on the trunk and head than on the extremities. 

However, an atypical presentation may occasionally develop. For instance, sun exposure can predispose to an atypical varicella rash, etc. Therefore, a study published in the Journal Acta Paediatrica aimed at systematically assessing the characteristics of cases affected by atypical primary varicella rash.

For the study, the United States National Library of Medicine, Excerpta Medica, and Web of Science databases were reviewed, without date or language restrictions. Articles were eligible if reporting previously healthy and immunocompetent subjects with a primary varicella rash (i.e., photo-localized primary varicella or skin inflammation‐associated primary varicella).

The findings of the study showed that out of 59 cases of atypical primary varicella, only 24 cases (median 8.5 years of age, 19 females) were photo-localized and 35 (median 4.8 years of age, 15 females) were associated with pre‐existing skin inflammation (including cast occlusion, diaper irritation, operative sites, burns, insect bites, vaccinations, or pre‐existing skin disease). The skin rash was monomorphic and without a “starry sky” appearance. The study also showed that irritants such as sun exposure or pre‐existing skin inflammation may modulate the distribution of varicella rash in previously healthy subjects.

While looking at the mechanism by which sun exposure or skin inflammation may modulate the distribution and the characteristics of varicella, it was postulated that sun exposure and skin trauma increase capillary permeability and activate the local inflammatory cycle. Furthermore, sun radiation favors the secretion of cytokines, which may have modulated the distribution and the type of rash.

As a result, it was concluded that primary varicella may have a modified presentation in areas of irritation such as sun exposure or inflammation caused by cast occlusion, diaper irritation, operative sites, burns, insect bites, vaccinations, or pre‐existing skin disease. There is a need for a wider awareness among clinicians of these modulators of viral skin diseases.

Source: Acta Paediatrica. 2022 May;111(5):935-9. DOI: https://doi.org/10.1111/apa.16300