New concepts on erythema annulare centrifugum: a clinical reaction pattern that does not represent a specific clinicopathological entity.

ABSTRACT

BACKGROUND: Erythema annulare centrifugum (EAC) is considered an inflammatory skin disease with unknown aetiology. In most textbooks it is assigned to the incoherent conglomeration of figurate or gyrate erythemas. OBJECTIVES: To re-evaluate a large cohort of patients with EAC and to assess the evidence for infection with Borrelia. METHODS: We retrospectively investigated 90 cases with the diagnosis of EAC. Haematoxylin and eosin sections were re-examined and diagnoses were specified; these were then confirmed by clinicopathological correlation. Infection with Borrelia was assessed by focus-floating microscopy and by a Borrelia-specific polymerase chain reaction (PCR). RESULTS: Besides a miscellaneous group of annular disorders at times confused with EAC such as urticaria, leucocytoclastic vasculitis and psoriasis (20 of 90; 22%), EAC appeared to serve as a collective term for three main clinicopathological reaction patterns (i) (tumid) lupus erythematosus (29 of 90; 32%), (ii) spongiotic dermatitides (25 of 90; 28%) and (iii) pseudolymphoma (16 of 90; 18%). In 13 of 16 (81%) cases with a pseudolymphomatous reaction pattern spirochaetes stained positive but were negative in other reaction patterns of EAC as well as in negative controls. These findings were confirmed by a Borrelia-specific PCR which was positive in two of three (67%) of these pseudolymphomatous EAC cases but was negative in all other variants of EAC (none of five) as well as 20 controls. CONCLUSIONS: We conclude that 'EAC' is a clinical reaction pattern that does not represent a specific clinicopathological entity and should lead to consideration of mainly lupus erythematosus, dermatitis and, in some cases, cutaneous Lyme disease.