Panniculitis With Histiocytoid/Immature Neutrophils is Not Limited to Histiocytoid Panniculitic Sweet Syndrome

Abstract

To the Editor: Dr. Chow et al have recently reported a series of patients with infiltrates of immature neutrophils involving either the dermis or subcutis. Cases involving the subcutis were referred to as subcutaneous histiocytoid Sweet syndrome. Whereas we have also made the diagnosis of histiocytoid Sweet syndrome in patients with immature infiltrates of neutrophils involving the dermis, we advise caution in the use of this term in those cases with immature neutrophils involving the subcutis, for a variety of reasons. Just as our understanding of panniculitis over the last decades has revealed Weber-Christian to be a wastebasket term consisting of a variety of previously poorly understood panniculitidies, neutrophilic infiltrates, whether consisting of mature or immature cells in the panniculis, may be seen with a variety of panniculities and do not necessarily warrant a diagnosis of Sweet or histiocytoid Sweet syndrome. In response to the report from Cohen1 in 2004 on subcutaneous Sweet syndrome, we reported the importance of excluding alpha-1-antitrypsin panniculitis, which can present as a neutrophilic panniculitis in patients with no other systemic signs of alpha-1-antitrypsin disease.2,3 Additionally, Thurber and Kohler4 have reported a neutrophilic dense pattern of erythema nodosum. Neutrophilic lobular panniculitis can also be seen in the infectious variant of neutrophilic eccrine hidradenitis. Pancreatic panniculitis may show mostly neutrophils without saponification and ghost cells in the earliest stages. Many of the reports on subcutaneous panniculitic T cell lymphomas have also mentioned prominent neutrophilic infiltrates masking the lymphomatous cells.5 Also important, patients with inflammatory bowel disease may frequently have subcutaneous neutrophilic infiltrates. Further, poststeroid panniculitis, which is often granulomatous, may also have dense neutrophils. Additionally, in our experience, patients with subcutaneous infiltrates of neutrophils rarely meet all the criteria for Sweet syndrome. Hence, just as in patients with subcutaneous infiltrates of mature neutrophils, when evaluating a patient with subcutaneous infiltrates of immature neutrophils, it is important to exclude the above-mentioned possibilities, and histiocytoid Sweet syndrome should be a diagnosis of exclusion. Pedram Gerami, MD Joan Guitart, MD Northwestern University Feinberg School of Medicine, Chicago, IL