Reply To the Editor

Reply

To the Editor,

Re: Dasanu et al. Muehrcke's lines (Leukonychiastriata) due to transretinoic acid therapy for acute promyelocytic leukemia. J Oncol Pharm Pract, published 2013, 19(4): 377–379. DOI:10.1177/1078155212468923

Beau's lines versus Muehrcke's lines: One is never too old to learn

We are very happy that our previous publication illustrating a case of Muehrcke's lines of fingernails due to the use of all-transretinoic acid ¹ has sparked such a vivid interest and comments by Polat and Uzun. ² Notwithstanding, these authors believe that we faced a case of another dermatologic entity (Beau's lines) rather than Muehrcke's lines involving the fingernails. They also claim that they have “detected broken nail and grooves on the white nail plate” in our photograph, which does not correspond to the truth. We assure them that there were no grooves or broken nails present in our patient. Some nail irregularities they see in the presented photographs were likely caused by the patient herself when she removed her previous nail polish.

Furthermore, we are happy to clarify the definition of these two very different dermatologic entities for them. Described by the French physician Joseph Honoré Simon Beau in 1846, the Beau's lines should be clearly distinguished from Muehrcke's lines of the fingernails. ³ While Beau's lines are actual ridges and indentations in the nail plate, Muehrcke lines are areas of hypopigmentation without palpable ridges similar to the ones described in our report.^1,3 They affect the underlying nail bed, and not the nail itself. Beau's lines should also be distinguished from Mees' lines of the fingernails, which are areas of discoloration in the nail plate.

Beau's lines are horizontal, going across the nail, and should not be confused with vertical ridges going from the bottom of the nail out to the fingertip. These vertical lines seen in our patient are rather a natural consequence of aging.^1,4

We hope we have now clarified for Polat and Uzun that we described a classic case of Muehrcke's lines, thereby enriching the scientific literature with a yet another intriguing skin side effect of the all-transretinoic acid.