Neutrophilic dermatoses.

Neutrophilic dermatoses (ND) are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. ND are classified based upon the localization of neutrophils within the skin and clinical features. Recent findings suggest that ND are due to two main mechanisms: i) a polyclonal hereditary activation of the innate immune system (polygenic or monogenic); or ii) a clonal somatic activation of myeloid cells such as encountered in myelodysplastic syndrome or VEXAS syndrome. ND belong to internal medicine as a great number of patients with ND suffer from an underlying condition (such as hematological malignancy, inflammatory bowel disease, auto-immune and auto-inflammatory diseases). ND are diagnoses of exclusion and physicians should always consider differential diagnoses, particularly skin infections. Here, we review the pathophysiology and classification of the main ND (i.e., subcorneal pustular dermatosis (Sneddon-Wilkinson Disease) and Intercellular IgA dermatoses, aseptic pustulosis of the folds, Sweet syndrome, neutrophilic eccrine hidradenitis, pyoderma gangrenosum, erythema elevatum diutinum, neutrophilic urticarial dermatosis and neutrophilic panniculitis), their clinical and histopathological features, and we highlight the investigations that are useful to identify ND-associated diseases and to exclude the differential diagnoses.

Type I interferon response and vascular alteration in chilblain-like lesions during the COVID-19 outbreak.

BACKGROUND: The outbreak of chilblain-like lesions (CLL) during the COVID-19 pandemic has been reported extensively, potentially related to SARS-CoV-2 infection, yet its underlying pathophysiology is unclear. OBJECTIVES: To study skin and blood endothelial and immune system activation in CLL in comparison with healthy controls and seasonal chilblains (SC), defined as cold-induced sporadic chilblains occurring during 2015 and 2019 with exclusion of chilblain lupus. METHODS: This observational study was conducted during 9-16 April 2020 at Saint-Louis Hospital, Paris, France. All patients referred with CLL seen during this period of the COVID-19 pandemic were included in this study. We excluded patients with a history of chilblains or chilblain lupus. Fifty patients were included. RESULTS: Histological patterns were similar and transcriptomic signatures overlapped in both the CLL and SC groups, with type I interferon polarization and a cytotoxic-natural killer gene signature. CLL were characterized by higher IgA tissue deposition and more significant transcriptomic activation of complement and angiogenesis factors compared with SC. We observed in CLL a systemic immune response associated with IgA antineutrophil cytoplasmic antibodies in 73% of patients, and elevated type I interferon blood signature in comparison with healthy controls. Finally, using blood biomarkers related to endothelial dysfunction and activation, and to angiogenesis or endothelial progenitor cell mobilization, we confirmed endothelial dysfunction in CLL. CONCLUSIONS: Our findings support an activation loop in the skin in CLL associated with endothelial alteration and immune infiltration of cytotoxic and type I IFN-polarized cells leading to clinical manifestations.

[Cutaneous plasmacytosis with Darier's sign in a woman of European origin]. / Plasmocytose cutanée avec signe de Darier chez une femme d'ascendance européenne.

INTRODUCTION: Cutaneous plasmacytosis is a rare skin condition first described in 1976 and it is seen mainly in patients of Asian descent. Patients usually present with multiple reddish-brown macules and nodules chiefly on the trunk and face, with clusters of well-differentiated plasma cells in the dermis. The aetiopathogenesis and nosological features of this entity remain obscure. We report herein a case of cutaneous plasmacytosis in a European middle-aged woman with presence of Darier's sign. PATIENTS AND METHODS: A 56-year-old woman of European descent presented with asymptomatic hyperpigmented patches affecting the dorsal aspect of her trunk for at least two years. Darier's sign was present in some episodes. Cutaneous biopsy showed a moderately dense interstitial and perivascular infiltrate containing numerous well-differentiated mature plasma cells affecting the entire dermal surface. Kappa and lambda immunochemistry demonstrated polyclonal plasma cell infiltrates with absence of light-chain restriction. Immunohistochemical examination was negative for HHV-8 and Treponema pallidum spirochetes. Laboratory findings revealed hypergammaglobulinaemia with no monoclonal bands being detected on immunofixation. A diagnosis of cutaneous plasmacytosis was made. In the absence of systemic involvement initial management consisted of clinical surveillance. DISCUSSION: The characteristic clinico-pathological features of CP allowed diagnosis of this skin condition in our patient, although it is very rarely reported in patients of European descent. The main differential diagnoses were ruled out, namely plasmacytic infiltrates related to infections and marginal B-cell lymphoma.