Muehrcke's nails, Muehrcke's lines, or leukonychia striata, are changes in the fingernail that may be a sign of an underlying medical disorder or condition. Muehrcke's lines are white lines (leukonychia) that extend all the way across the nail and lie parallel to the lunula (half moon). In contrast to Beau's lines, they are not grooved. The lines are actually in the vascular nail bed underneath the nail plate, and as such, they do not move with nail growth. Meuhrcke's lines disappear when pressure is placed over the nail, blanching the underlying nail bed.
The appearance of Muehrcke's lines is nonspecific, but they are often associated with decreased protein synthesis, which may occur during periods of metabolic stress (e.g., after chemotherapy) and in hypoalbuminemic states such as the nephrotic syndrome.:659
An example of Muehrcke's lines in the context of chemotherapy was published in the New England Journal of Medicine in 2007. 
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- Muehrcke Lines of the Fingernails at eMedicine
- Muehrcke's Lines of the Fingernails on WebMD
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