Erythema Elevatum Diutinum
Erythema elevatum diutinum (EED) is a rare type of localized cutaneous small vessel vasculitis, characterized by a chronic, fibrosing course. EED is primarily seen in patients in the fourth to sixth decades, though a few paediatric cases have been reported [1,2]. The condition typically presents with symmetrical, red-brown to violaceous papules and plaques overlying joints, tendons and extensor surfaces. Lesions tend to persist for years, becoming firm and nodular, with a pink-yellow coloration resembling xanthomata. EED is thought to be due to immune complex disease and frequently can be associated with underlying medical conditions, specifically autoimmune disease, bacterial infections and hypergammaglobulinaemia (primarily IgA) or paraproteinaemia.
Erythema elevatum diutinum was first described in the late 19th century by Hutchinson  and the descriptive terminology – indicating redness, raised plaques and characteristic persistence of the lesions – appeared in the literature in1894 . Most of the patients described at this time were middle-aged men. In 1889 Bury reported the first case in a 12-year-old girl  while Radcliffe-Crocker & Williams later described a 6-year-old girl with similar findings, coining the term ‘erythema elevatum diutinum’ . Subsequently, cases in younger females were labelled as the Bury type, whereas the so-called Hutchinson type occurred primarily in middle-aged to elderly men with gout . Current evidence suggests that the conditions are one and the same, therefore this subclassification is no longer used.
Of historical interest, there was significant confusion in the medical literature regarding the relationship between EED and granuloma annulare, which were considered different manifestations of the same condition when first reported . Subsequently, in 1910, Dalla-Favera definitively distinguished the two conditions based on their characteristic histopathology  and these findings were further substantiated by Piccardi . Additionally, in the 1930s, cases of persistent, red-orange plaques and nodules on the extremities, buttocks and face were labelled as a new condition called ‘extracellular cholesterolosis’ due to prominent lipid deposits within the dermis . This term is obsolete as it is thought to represent a chronic form of EED .
Erythema elevatum diutinum most often presents with symmetrical, firm, red, red-brown or violaceous persistent papules, plaques or nodules which may coalesce and slowly enlarge. Most cases are asymptomatic, though pruritus, burning sensation and tenderness may characterize early lesions. The most commonly involved locations include the extensor aspects of the extremities, specifically over joints and tendons. Lesions involving the trunk, retro-auricular scalp, palms and soles have also been reported . Affected areas may occasionally ulcerate and heal with atrophy or dyspigmentation, or display variation during the day. Interestingly, some patients report that lesions become more erythematous and indurated at night .
Although the exact cause of erythema elevatum diutinum is unknown, it may represent a form of immune complex-mediated small vessel vasculitis, possibly induced by chronic antigen exposure. Intermittent or repeated bouts of immune complex deposition followed by activation of the complement cascade, inflammation and incomplete resolution may ultimately lead to the chronic changes and persistent fibrotic response seen in EED. More specifically, C5a and other inflammatory mediators recruit neutrophils to the affected areas during the acute inflammatory response, and thereafter the release of lysosomal enzymes by neutrophils mediates the tissue damage seen .