We hope this Notable Note will bring you some holiday cheer as we discuss one of medicine’s most delightful eponyms: the famed “Christmas tree” distribution of the secondary lesions found in pityriasis rosea. Every student of dermatology learns this eponym, which is mentioned in nearly all contemporary textbooks of dermatology. Surprisingly, none of these references offer any discussion on the origin of the term. Where did the Christmas tree eponym come from?
To answer this question, we reviewed numerous textbooks of dermatology and review articles on pityriasis rosea going back over 100 years and found no mention of the Christmas tree eponym before the 1950s. However, we did find another eponym from 1935 that describes the same phenomenon as the Christmas tree distribution but was called “le signe du baldaquin” (“the baldaquin sign”). It was proposed by 2 dermatologists at Lyon, France: Joseph Nicolas (1868-1960) and Jean Rousset (1899-1972).1 They noticed, like other dermatologists of their time, that the secondary lesions of pityriasis rosea oriented themselves with their long axes along the Langer lines of skin cleavage (Karl Langer, 1819-1887). Nicolas and Rousset suggested that the pattern formed by the obliquely downward direction of the skin lesions resembled the looped curtain folds of a baldaquin (canopy) (Figure) and was a finding of diagnostic significance. The baldaquin sign enjoyed a limited popularity in the dermatology literature but was ultimately replaced by the Christmas tree eponym.
Burgdorf WHC, Plewig G, Lipsker D, Hoenig LJ. The Mystery of the Christmas Tree. JAMA Dermatol. 2016;152(12):1405. doi:10.1001/jamadermatol.2015.0809