Eosinophilic Dermatoses: Recognition and Management

Eosinophilic dermatoses encompass a broad spectrum of diseases of different etiologies hallmarked by eosinophilic infiltration of the skin and/or mucous membranes, with or without associated blood eosinophilia. The wide range of dermatological manifestations of this spectrum, including nodules and plaques, pustules, blisters, ulcers, and urticarial lesions, is reflected in a non-univocal classification system. We identified six groups of eosinophilic dermatoses based on the predominant anatomic level of involvement: (1) epidermal; (2) of the dermal-epidermal junction; (3) dermal; (4) of the hypodermis and muscle fascia; (5) of the pilosebaceous unit; and (6) vascular/perivascular. We review clinicopathologic features and management of diseases belonging to each group, particularly: (1) pemphigus herpetiformis and atopic dermatitis as prototypes of the epidermal group; (2) bullous pemphigoid as prototypic eosinophilic dermatosis of the dermal-epidermal junction; (3) eosinophilic cellulitis (Wells syndrome), hypereosinophilic syndromes, Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, eosinophilic dermatosis of hematologic malignancy and chronic spontaneous urticaria as paradigmatic dermal eosinophilic dermatoses; (4) eosinophilic fasciitis as an eosinophilic dermatosis with predominant involvement of the hypodermis and muscle fascia; (5) eosinophilic pustular folliculitis as a model of the pilosebaceous unit involvement; and (6) granuloma faciale, angiolymphoid hyperplasia with eosinophilia, and eosinophilic granulomatosis with polyangiitis, belonging to the vascular/perivascular group.

Mepolizumab for the treatment of eosinophilic granulomatosis with polyangiitis

INTRODUCTION

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterized by asthma, hypereosinophilia, and progressive multiorgan involvement. Although not fully elucidated, advancement in our understanding of the pathophysiology of EGPA has led to the development of multiple new treatment targets.

AREAS COVERED

Herein we review the epidemiology, clinical manifestations, pathophysiology, treatments, and ongoing research in the management of EGPA. The central role of Interleukin-5 (IL-5) in the development and maintenance of hypereosinophilia will be discussed. The value of mepolizumab, an anti-IL-5 monoclonal antibody, in the treatment of EGPA is reviewed in detail.

EXPERT OPINION

The available literature supports the use of mepolizumab for the induction and maintenance of remission of refractory, relapsing, or glucocorticoid-dependent EGPA with potentially greater benefit in those who are ANCA-positive or those with greater eosinophilia ( ≥ 150 cells/ μ L). Despite these positive results, relapses remain frequent, and the need for both short- and long-term glucocorticoid use remains common. More research is needed to address these needs and determine the precise role of mepolizumab.

Optimal therapy and prospects for new medicines in eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)

INTRODUCTION

The prevalence of eosinophilic granulomatosis with polyangiitis (EGPA; previously known as Churg-Strauss syndrome) is lower than that of other antineutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV's), and only a few randomized controlled trials have been conducted for this rare disease. However, recent international efforts have helped delineate the best treatment approach.

AREAS COVERED

At present, EGPA conventional therapy is by default similar to that of other AAVs. Limited, non-severe EGPA can initially be treated with glucocorticoids (GCs) alone. Patients with life-threatening manifestations and/or major organ involvement must receive a combination of GCs and an immunosuppressant, mainly cyclophosphamide. Remission can be achieved in >85% of patients with these first-line treatments, but vasculitis relapses occur in more than one-third of patients, and about 85% cannot stop GC treatment because of GC-dependent asthma and/or ENT manifestations. A few biologic agents, including rituximab or mepolizumab, are now under investigation after interesting preliminary results. Expert commentary: Treatment for EGPA still has several unmet needs. Several biologic agents are now under investigation in randomized controlled trials, but a few others should be considered soon. Their benefit should be demonstrated for devising more EGPA-tailored therapeutic strategies (ideally GC-free).

Churg-Strauss syndrome

Churg-Strauss syndrome (CSS), alternatively known as eosinophilic granulomatosis with polyangiitis (EGPA), was first described in 1951 by Churg and Strauss as a rare disease characterized by disseminated necrotizing vasculitis with extravascular granulomas occurring exclusively among patients with asthma and tissue eosinophilia. EGPA is classified as a small-vessel vasculitis associated with antineutrophil cytoplasmic antibodies (ANCAs) and the hypereosinophilic syndromes (HESs) in which vessel inflammation and eosinophilic proliferation are thought to contribute to organ damage. Although still considered an idiopathic condition, EGPA is classically considered a Th2-mediated disease. Emerging clinical observations provide compelling evidence that ANCAs are primarily and directly involved in the pathogenesis of AASVs, although recent evidence implicates B cells and the humoral response as further contributors to EGPA pathogenesis. EGPA has traditionally been described as evolving through a prodromic phase characterized by asthma and rhino-sinusitis, an eosinophilic phase marked by peripheral eosinophilia and organ involvement, and a vasculitic phase with clinical manifestations due to small-vessel vasculitis. The American College of Rheumatology defined the classification criteria to distinguish the different types of vasculitides and identified six criteria for EGPA. When four or more of these criteria are met, vasculitis can be classified as EGPA. The French Vasculitis Study Group has identified five prognostic factors that make up the so-called five-factor score (FFS). Patients without poor prognosis factors (FFS=0) have better survival rates than patients with poor prognosis factors (FFS≥1). The treatment of patients with CSS must be tailored to individual patients according to the presence of poor prognostic factors. A combination of high-dose corticosteroids and cyclophosphamide is still the gold standard for the treatment of severe cases, but the use of biological agents such as rituximab or mepolizumab seems to be a promising therapeutic alternative.