What is the pathophysiology of eosinophilic fasciitis (EF)?

Updated: Dec 24, 2020
  • Author: Peter M Henning, DO; Chief Editor: Herbert S Diamond, MD  more...
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Although the etiology of eosinophilic fasciitis is unknown, studies have shed light on some of the mechanisms involved in its pathogenesis.

In general, the pathophysiology underlying eosinophilic fasciitis is postulated to involve an inflammatory response resulting in an activated inflammatory cell infiltrate of affected tissues and subsequent dysregulation of extracellular matrix production by lesional fibroblasts.

Viallard et al demonstrated that, when stimulated, peripheral blood mononuclear cells of eosinophilic fasciitis patients produce significantly higher amounts of five cytokines, including interleukin (IL)–5 and interferon (IFN)–gamma. [7] IL-5 is known to activate mature eosinophils and to stimulate eosinophil chemotaxis, growth, and differentiation. IFN-gamma activates tissue macrophages and T cells. The findings of Dziadzio et al support increased levels of IL-5 in eosinophilic fasciitis, in addition to increased levels of transforming growth factor (TGF)–beta, another fibrogenic cytokine. [8]

Toquet et al investigated the phenotype of the lesional inflammatory cell infiltrate in patients with eosinophilic fasciitis and demonstrated a predominance of macrophages, CD8+ lymphocytes, and few eosinophils. [9] Pathologic specimens from patients with eosinophilic fasciitis demonstrate increased numbers of eosinophils, especially early in the disease course.

Taken together, the findings of these studies suggest a mechanistic framework marked by a proinflammatory and fibrogenic cytokine response with resultant tissue inflammatory cell infiltration.

In the tissues, the end effector cell of fibrosis is the fibroblast. Fibroblasts from lesional tissue of patients with eosinophilic fasciitis produce excess collagen in vitro and display elevated TGF-beta and type 1 collagen mRNA levels when examined via in situ hybridization with specific cDNA. [10, 11] Therefore, the pathogenesis appears to involve the concomitant increase in the expression of genes for TGF-beta and extracellular matrix proteins in fibroblasts in the affected tissues.

Mori et al suggested that an autocrine stimulatory loop involving major basic protein, a product of eosinophil degranulation, IL-6, which enhances collagen production and is induced my major basic protein, and TGF-beta could account for the progressive fibrosis seen in several eosinophil prominent disorders. [12]

Other studies showed elevated levels of serum manganese superoxide dismutase and tissue metalloproteinase 1 (TIMP-1) in eosinophilic fasciitis, suggesting a role in pathogenesis and providing a possible marker of disease activity. [13]

Fasciitis may be a common manifestation of various pathophysiologic processes associated with eosinophilia. The existence of primary and secondary forms of fasciitis has recently been suggested.

Understanding the mechanisms involved in the development of fascial inflammation and fibrosis in these conditions may yield insights into the pathogenesis of other fibrotic skin diseases.

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