Major cluster of paediatric ‘true’ primary chilblains during the COVID-19 pandemic: a consequence of lifestyle changes due to lockdown

Background: Over the last months, during the COVID-19 pandemic, a growing number of chilblain-like lesions were reported mainly in children and rarely in young adults. The relationship with SARS-CoV-2 infection was postulated, often without any laboratory, instrumental or clinical confirmation. The disclosure of information about chilblain-like lesions as a COVID-19 manifestation in social media has created concern in children’s families and paediatricians. Objectives: To verify whether the chilblain-like lesions were caused by SARS-CoV-2 infection. Methods: Prospective study on a case series including children who presented with acral lesions at the Pediatric Dermatology Outpatient and Pediatric Emergency Unit of the University of Bologna, from 1 April to 30 April 2020. We reported demographical, laboratory and clinical features, history of close contact with COVID-19 patients, presence of similar skin lesions in other family members, precipitating and risk factors for chilblain onset. Results: We evaluated eight patients (five females, three males) aged between 11 and 15 years. We excluded acute or previous SARS-CoV-2 infection with RT-PCR nasopharyngeal swab, serum antibody levels using chemiluminescent immunoassays. Other acute infections causing purpuric lesions at the extremities were negative in all patients. Skin lesion biopsy for histological and immunohistochemical evaluation was made in two cases and was consistent with chilblain. PCR assay on skin lesion biopsy for parvovirus B19, Mycoplasma pneumoniae and SARS-CoV-2 was performed in a patient and resulted negative. We identified common precipitating and risk factors: physical (cold and wet extremities, low BMI), cold and wet indoor and outdoor environment, behaviours, habits and lifestyle. We therefore reached a diagnosis of primary chilblains. Conclusions: During the COVID-19 pandemic, a ‘cluster’ of primary chilblains developed in predisposed subjects, mainly teenagers, due to cold exposure in the lockdown period. Laboratory findings support our hypothesis, although it is also possible that an unknown infectious trigger may have contributed to the pathogenesis.