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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). [ABSTRACT FROM AUTHOR]

Autoinflammation is defined by aberrant, antigen-independent activation of the innate immune signaling pathways. This leads to increased, pro-inflammatory cytokine expression and subsequent inflammation. In contrast, autoimmune and allergic diseases are antigen-directed immune responses from activation of the adaptive immune system. The innate and adaptive immune signaling pathways are closely interconnected. The group of 'complex multigenic diseases' are a result of mutual dysregulation of both the autoinflammatory and autoimmune physiologic components. In contrast, monogenic autoinflammatory syndromes (MAIS) result from single mutations and are exclusively autoinflammatory in their pathogenesis. Studying the clinical and histopathological findings for the various MAIS explains the phenotypical correlates of their specific mutations. This review aims to group the histopathologic clues for autoinflammation into three recognizable patterns. The presence of these histologic patterns in a pediatric patient with recurrent fevers and systemic inflammation should raise suspicion of an autoinflammatory component in MAIS, or, more frequently, in a complex multigenic disease. The three major histopathological patterns seen in autoinflammation are as follows: (i) the 'neutrophilic' pattern, seen in urticarial neutrophilic dermatosis, pustular psoriasis, aseptic neutrophilic folliculitis, and Sweet's syndrome; (ii) the 'vasculitic' pattern seen in small vessel-vasculitis (including hypersensitivity/leukocytoclastic vasculitis, thrombosing microangiopathy and lymphocytic vasculitis), and intermediate-sized vessel vasculitis, mimicking polyarteritis nodosa; and (iii) the 'granulomatous' pattern. Beyond these three patterns, there are additional histopathologic clues, which are detailed below. It is important for a dermatopathologist to recognize the patterns of autoinflammation, so that a diagnosis of MAIS or complex multigenic diseases may be obtained. Finally, careful histopathologic analyses could contribute to a better understanding of the various clinical manifestations of autoinflammation. [ABSTRACT FROM AUTHOR]

Dear Editor, Deficiency of interleukin-36 receptor antagonist (DITRA) syndrome is an autoinflammatory disease caused by loss of function mutations in the interleukin-36 receptor. We report the case of a boy suffering from DITRA syndrome and a novel mutation in the I IL36RN i gene. DITRA syndrome is a life-threatening autoinflammatory disease first described by Marrakchi et al.1 Homozygous or compound heterozygous loss-of-function mutations responsible for DITRA may be inherited or arise de novo, and both missense and nonsense pathogenic variants have been reported.2 The c.227C > T (p. Pro76Leu) variant has already been described as pathogenic. [Extracted from the article]

Abstract: When dealing with nails, pathologic examination is often indispensable to reach an accurate diagnosis. This requires a biopsy correctly performed by the dermatologist, a specimen correctly handled in the pathology lab, and a pathologist with good knowledge of the various nail conditions. The normal nail histology is first described in this paper. The pathologic aspects of melanocytic lesions, nonmelanocytic tumors of the nail apparatus, inflammatory nail conditions, and onychomycosis are then considered, together with their main differential diagnoses. [Copyright &y& Elsevier]

The etiology of longitudinal melanonychia (LM) is difficult to establish by clinical and dermoscopic examinations alone. Microscopic examination of the nail matrix remains crucial. Two groups of LM may be identified: melanocytic activation (melanic pigmentation of the matrix epithelium without any increase in the density of melanocytes) and melanocytic proliferation (lentigo, nevus, or melanoma). The histological examination is challenging, and immunohistochemical investigations can be helpful. The objective of this study was to analyze the immunohistochemical findings with routinely used markers in melanocytic tumors-S-100 protein, HMB-45, and Melan-A-in LM. A series of 40 cases were analyzed: 10 activations, 4 lentigines, 7 nevi, 12 in situ melanomas, and 7 invasive melanomas. The sensitivity of S-100 protein is weak in benign and malignant intraepithelial melanocytes of the nail matrix, and if this marker is performed alone, it may be wrongly reassuring. However, the use of S-100 protein is essential to differentiate invasive melanoma, lacking an intraepithelial component, and particularly desmoplastic melanoma, from epithelial and mesenchymal tumors. HMB-45 and Melan-A are more sensitive than S-100 protein for the evaluation of intraepithelial melanocytic proliferation of the nail apparatus, with HMB-45 being the most intense marker. In the dermal component, HMB-45 and Melan-A were less sensitive than S-100 protein. In conclusion, we recommend that the panel of antibodies used for histological evaluation of LM should include HMB-45 and/or Melan-A and S-100 protein only if an invasive melanoma is suspected.

POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin disorders) is a rare multisystemic disease associated with plasma cell dyscrasia. A 68-year-old woman with chronic renal insufficiency and arterial hypertension included in her medical history was admitted to the hospital with confusion, somnolence and asthenia. She presented ascites, hepatosplenomegaly, leg oedema, distal dysesthesias, leuconychia and multiple nodular purple red angiomas on the trunk, upper limbs and fingers. Hypothyroidism was revealed in the laboratory investigations and monoclonal IgG peak in immunoelectrophoresis. Electromyography showed both demyelinisating and axonal degenerative neuropathy. The diagnosis of POEMS syndrome was based on the dermatopathological examination of a cutaneous angioma; histology revealed features of glomeruloid angioma, a specific marker of this syndrome., (Copyright 2002 S. Karger AG, Basel)