Diagnosis: Dermal Infiltrate of Neutrophils
• Neutrophilic dermatoses are a clinically heterogeneous group of entities characterized by the presence of a dense dermal infiltrate of neutrophils with variable leukocytoclasis, lack of microorganisms on special stains and cultures, and clinical improvement after systemic steroid therapy.
• The entities in neutrophilic dermatoses include acute febrile neutrophilic dermatosis (Sweet syndrome), pyoderma gangrenosum, rheumatoid neutrophilic dermatosis, bowel-associated dermatosis syndrome, and Behçet disease.
• Four clinical subtypes of pyoderma gangrenosum have been described: ulcerative pyoderma gangrenosum with an undermined border, pustular pyoderma gangrenosum with discrete painful pustules, bullous pyoderma gangrenosum with painful bullae, and vegetative pyoderma gangrenosum with painless ulcers and a nonundermined exophytic border.
• The earliest lesion of ulcerative pyoderma gangrenosum shows a sterile follicular and perifollicular neutrophilic abscess, which is rarely seen in Sweet syndrome. In later lesions, there is necrosis of the superficial dermis and epidermis forming an ulcer, the base of which shows a mixed inflammatory cell infiltrate with abscess formation.
• Wells syndrome (eosinophilic cellulitis) manifests as an indurated cellulitis-like plaque, with multiple potential triggers. The flame figures seen in Wells syndrome consist of eosinophil granule major basic protein deposited on otherwise normal collagen. This tissue reaction may be seen in several conditions with a massive eosinophilic infiltrate, including arthropod reactions, parasitic infestations, bullous pemphigoid, and eosinophilic ulcer of the oral mucosa.
