Muehrcke's nails

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.