Background: The abundance of publications of COVID-19-induced chilblains has resulted in a confusing situation. Methods: This is a prospective single-institution study from 15 March to 13 May 2020. Thirty-two patients received PCR nasopharyngeal swabs. Of these, 28 patients had a thoracic CT-scan, 31 patients had blood and urine examinations, 24 patients had skin biopsies including immunohistochemical and direct immunofluorescence studies, and four patients had electron microscopy. Results: COVID-19-induced chilblains are clinically and histopathologically identical to chilblains from other causes. Although intravascular thrombi are sometimes observed, no patient had a systemic coagulopathy or severe clinical course. The exhaustive clinical, radiological, and laboratory work-up in this study ruled-out other primary and secondary causes. Electron microscopy revealed rare, probable viral particles whose core and spikes measured from 120 to 133 nm within endothelium and eccrine glands in two cases. Conclusion: This study provides further clinicopathologic evidence of COVID-19-related chilblains. Negative PCR and antibody tests do not rule-out infection. Chilblains represent a good prognosis, occurring later in the disease course. No systemic coagulopathy was identified in any patient. Patients presenting with acral lesions should be isolated, and chilblains should be distinguished from thrombotic lesions (livedo racemosa, retiform purpura, or ischemic acral necrosis).

Immunotherapy has become the standard of care for various cancer types. The widespread use of immune checkpoints inhibitors confronts us with a whole range of novel immune-related adverse events. Skin toxicity is one of the most frequent adverse events. In this article, we report a case of anti-PD-1 induced late bullous pemphigoid (BP) with mucosal erosions and associated with a troublesome neurological disorder of undetermined origin in a patient with metastatic melanoma. Skin biopsy was essential to make the diagnosis and rapid initiation of systemic prednisolone played a role in favorable clinical outcome of BP. We will discuss the difficulty of early diagnosis of BP, its unusual association with neurological disorders, and the specific management of this particular dermatological entity.