Erythema annulare centrifugum", spelled with 2 "N", is a noun that has unfortunately largely replaced the regular Latinized disease term "erythema anulare centrifugum" in the international literature (note: see there for details on erythema anulare centrifugum ).
PubMed shows only 22 hits for the search term "erythema anulare centrifugum", but 319 hits for the search term "erythema annulare centrifugum". If you look at the German-language textbooks by Otto Braun-Falco via Peter Fritsch and Thomas Dirschka (Klinikleitfaden), the completely correct spelling with an N is retained.
But how did this linguistic "mistake" actually come about? In fact, Jean Darier was the originator of this cause célèbre. In 1916, Darier described an exanthema under the name "l'érythème papulo-circineé migrateur et chronique", and in a more catchy, completely correctly spelled French abbreviated form "l'érythème annulaire centrifugue". It should be noted that annular is translated as "annulaire" in French and as "annular" in English, i.e. with two "N "s in each case. In Latin, on the other hand, annular is translated as "annulus", written with one N.
This means that "erythema anulare centrifugum" is correctly written with just one "N" in the Latinized spelling. However, since in medicine people vote with their feet, it can be predicted that the original spelling "Erythema anulare centrifugum" will give way to the Anglicized spelling "Erythema annulare centrifugum".