Erythema Elevatum Diutinum

This rare condition is characterized by persistent, initially red to violaceous and later brown to yellow papules, nodules, and plaques . The lesions, typically distributed symmetrically on the extensor surfaces of the extremities, are initially soft and then evolve into fibrous nodules.

Histopathologic Features.

In the early stage of EED, nonspecific LeV is observed. In later stages, granulation tissue and fibrosis form with a diffuse mixed-cell infiltrate showing a predominance of neutrophils. The capillaries may still show deposits of fibrinoid material or merely fibrous thickening. Fully developed lesions of EED may be indistinguishable from neutrophilic dermatoses discussed later, Behcet's disease, or neutrophilic drug reaction. Granuloma faciale may also resemble

EED but is distinguished by clinical localization to the face, sparing of the superficial papillary dermis (a grenz zone), and prominence of eosinophils and plasma cells in addition to neutrophils. Occasional cases show neutrophilic microabscesses in the tips of dermal papillae that might suggest dermatitis herpetiform is . In old, fibrotic lesions of EED there is an orderly array of spindle cells and collagen bundles often parallel to the skin surface with vertically arranged capillaries similar to a scar. Lipid material also may be present as cholesterol clefts. Serial sections may be required to demonstrate vascular damage in late lesions. These older lesions of EED must be differentiated from Kaposi's sarcoma, dermatofibroma, or granuloma annulare. Neutrophils, nuclear dust, and fibrin owing to persistent vascular damage may be present, helping to distinguish these lesions from dermatofibromas or scars. The irregularly arranged, jagged vascular spaces of Kaposi's sarcoma are absent, and many of the spindle cells have the immunohistochemical and electron microscopic features of macrophages. Focal areas of basophilic collagen caused by nuclear dust in EED can resemble the mucin seen in granuloma annulare but do not stain with Alcian blue.

pathogenesis