Background Confusion exists regarding interstitial granulomatous dermatitis (IGD) and palisaded neutrophilic and granulomatous dermatitis (PNGD). Objective To determine whether IGD and PNGD are two different entities, or whether they must be considered as two subtypes of the same reactive pattern, and thus whether the unification of the nomenclature is necessary. Methods Observational retrospective multicentre study of patients with IGD and PNGD evaluated between 1999 and 2019 and review of their clinical and histological features. Results We identified 52 patients (38 women and 14 men). Clinical and histological findings of IGD were observed in 88.4% of cases. The most common cutaneous lesions were plaques/macules (IGD) or annular plaques and papules/nodules (PNGD), located mostly on the limbs and trunk. The rope sign was developed in two patients with IGD that associated autoimmune disorders. Similar associated comorbidities (75%) were found in both entities, mainly autoimmune diseases (53.8%). In IGD, the infiltrate was predominantly lympho-histiocytic. Neutrophilic infiltrates, karyorrhexis and skin lesions with limited clinical course were mainly associated with PNGD biopsies. In biopsies with a limited recurrent course, a predominant lymphocytic inflammatory infiltrate was found. Collagen degeneration was present in 75.9% of cases. The floating sign was observed only in IGD type patients (63%). Overlapping histological findings were found in one fourth of cases, especia

Introduction: Parvovirus B19 (PVB19) infection has a high incidence and worldwide distribution. It has a broad clinical spectrum, with skin, joint and haematological manifestations being the most common. The objective of this study was to determine the epidemiology and clinical-analytical manifestations of acute PVB19 infection. Patients and methods: A retrospective study of patients with a positive IgM serology for PVB19 (10 years). Forty-six patients were included and their demographic, clinical and analytical characteristics were analyzed. Results: Primary infection was most prevalent in women (ratio 2.2:1) aged 41 (mean age). Joint involvement was the most common manifestation (65%). Skin abnormalities were observed in more than half of patients (24 cases): rash (28%), megalerythema (9%), "gloves and socks" involvement (6.5%), periflexural rash (4%) and oedema (4%). Anaemia was the main haematological alteration (35%). The symptoms were self-limiting and resolved in 1-2 weeks in most patients. Conclusions: Although there is a variable clinical spectrum, polyarthralgias and generalized maculopapular rash with fever and anaemia are the typical and most frequent manifestations of primary infection by PVB19 and are usually self-limiting.