Sweet’s syndrome and erythema nodosum: two neutrophilic dermatoses?

Abstract

Dear Editor, We have read with great interest the article by Wasson and Folzenlogen about the concurrent occurrence of Sweet’s syndrome (SS) and erythema nodosum (EN) [1]. We would like to state some observations about this article. We entirely agree that SS and EN share some features that closely link these two reactive dermatoses: inflammatory clinical picture with acute onset, common associated conditions as inflammatory bowel disease or streptococcal infection and response to similar therapeutic agents as systemic glucocorticoids or potassium iodide. Moreover, although EN is not considered as neutrophilic dermatosis, many cases of this condition can show, especially in their initial phases, a neutrophil-rich infiltrate [2–4]. These coincidences are additionally supported by the report of many patients with both conditions, not only concurrently, as it is usual, but also successively: there are patients who can react to the same stimulus sometimes with SS and sometimes with EN [5, 6]. All of these data support our conviction that EN could be included within the group of the neutrophilic dermatoses. In addition to the case reports about the association of SS and EN cited by Wasson and Folzenlogen, there are several case series of SS that show the association between these two dermatoses and, unlike that it is asseverated by those authors, these associations are supported by histopathological studies. In our case series of 16 patients with SS, 5 of them (31%) presented a biopsy-proven EN [7]. There also are at least two other case series of patients with SS showing biopsy-proven EN: Vanaclocha [8] and Sitjas et al. [9] reported that 25% and 30% of their patients with SS had EN, respectively. These studies underlined the idea that the association of SS and EN is more frequent than reported previously. We agree with Wasson and Folzenlogen that it is indispensable to make a histopathological confirmation of nodular lesions in patients with SS because these nodular lesions can reflect as much an EN as a neutrophilic panniculitis resulted from the spread of overlying dermal infiltrate. Other debated question is the significance of the occurrence of nodular lesions without typical SS because they can reflect both a subcutaneous SS (isolated neutrophilic panniculitis) and any other type of pannicultis with neutrophilic infiltrates [3, 10, 11]. In conclusion, the relationship between SS and EN is supported by four features: (1) the two conditions are reactive dermatoses to similar stimulus, (2) the clinical picture of both dermatoses can be similar when it is located on the legs, (3) the two conditions can appear simultaneously or sequentially in the same patient and (4) both respond to the same treatments. If we also consider that many EN have a septal neutrophilic infiltrate in the early stage, it is not a misbegotten idea that EN can be included within the group of neutrophilic dermatoses.