Neutrophilic panniculitis

Panniculitis is an inflammatory disorder of the subcutaneous fat, whose diagnosis and classification relies on histologic features, mainly the location of the subcutaneous inflammatory infiltrate (septal, lobular, mixed or vascular) [1]. In the setting of lobular panniculitis in which the inflammation predominantly involves the fat lobules, there is neutrophilic panniculitis (NP), a rare condition that belongs to the group of neutrophilic dermatoses [2]. Clinically, NP manifests as a subcutaneous nodular eruption and, histologically, shows a lobular infiltrate mainly consisting of neutrophils [3–7]. NP has been reported to be significantly associated with myelodysplasia, which is a well-known association for neutrophilic dermatoses in general [3–7]. From a therapeutic point of view, it is regarded as highly sensitive to oral corticosteroids, similarly to Sweet’s syndrome [2]. In this chapter, the clinical and histological features of NP are described, with emphasis on the differential diagnosis from the main panniculitides sharing a neutrophilic histological pattern.