The term "annular dermatoses" (AD) covers a large number of clinically and aetiogenetically heterogeneous skin diseases whose easily recognizable common feature is the initially punctiform or disc-shaped, later ring-shaped morphological structure of the centrifugally expanding lesions. The diagnosis is made clinically by taking an appropriate history and analyzing the clinical aspect (acute/chronic, isolated/multiple lesions, erythema/purpura, histological substrate, etc.). Diagnostic confirmation can be provided by microscopic findings (lymphocytic, eosinophilic, neutrophilic, lichenoid).
The ability of the skin to form anular structures is referred to below as "anularity". Anularity is defined as a characteristic, multiphasic, pathological reaction of the skin. Apart from the oral mucosa, anularity is not observed on other epithelial surfaces.
Basically, anularity can be divided into:
- Primary anularity
- and
- secondary anularity.
In primary anularity , the annular pattern is an intrinsic characteristic of the respective dermatosis, irrespective of its genesis, and defines it(erythema anulare centrifugum, erythema gyratum repens, erythema chronicum migrans, granuloma anulare, etc.).
In secondary anularity, the anular patterns occur more or less randomly among their other, different clinical manifestations. Their diagnostic value is therefore limited. The list of secondary anular erythema is long.