Histological Classification and Differential Diagnosis of Nonepisodic Angioedema With Eosinophilia: A Clinicopathologic Study of 12 Cases With Literature Review.

Nonepisodic angioedema with eosinophilia (NEAE) is a rare condition characterized with monoepisodic angioedema, a nonfebrile state, eosinophilia, normal serum IgM levels, and lack of internal organ involvement. The histology of this disease is not yet well known. The purpose of this study was to characterize the histopathologic features of NEAE. Twelve cases of clinically confirmed NEAE were retrieved from 6 institutions, and these cases were reviewed regarding the clinical data and histopathology, particularly regarding granulomatous lesions. The authors demonstrated that the histology of NEAE can be classified into 3 patterns that of eosinophilic granulomatous panniculitis (7/12 cases), eosinophilic dermatitis without granuloma formation (3/12 cases), and invisible dermatosis (2/12 cases). Six of the 7 granulomatous cases showed the characteristic eosinophilic granulomatous lesions containing individual necrotic adipocytes with membranous fat changes, which could be a differential clue to the diagnosis of NEAE. Review of the previously reported cases (n = 37) revealed that the histological classification could be adaptable to these reported cases. The authors should recognize the histological variation of NEAE and distinguish it from the histological mimickers, including eosinophilic granulomatosis with polyangiitis, erythema nodosum, hypereosinophilic syndrome, and episodic angioedema with eosinophilia.