M
maceration
Softened or broken down skin resulting from prolonged exposure to wetness causing whitening and thickening of the keratin sometimes with redness, oozing, and/or scaling.
macule
A flat, generally less than .5 cm area of skin or mucous membrane with different color from surrounding tissue. Macules may have non-palpable, fine scale.

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madarosis
A loss of the eyelashes or eyebrows.
marginal scale
See trailing edge scale.
Mee's lines
Transverse white line(s) in the nail plate that is non specific and can be seen with any severe systemic insult. They grow out with the nail plate. Often seen with arsenic ingestion.
meniscus of pus
Pus within a bulla often having a crescentic shape.
micaceous scale
Shiny, flat flakes resembling the mineral mica.
milia
Tiny white cysts, usually less than 2 mm, containing keratin.
moniliform
Resembling a string of beads.
morbilliform
Generalized, small erythematous macules and/or small papules resembling the rash of measles.
mottled
Marked with spots of different colors.
Muehrcke lines
Transverse white bands that are an abnormality of the nail bed and do not grow out with the nail. Muehrcke lines are commonly associated with hypoalbuminemia.
multilocular
Multiple chambers separated by septae.
N
nail bed
Epithelium and dermis beneath nail plate extending from the nail matrix to the hyponychium.
nail folds
The folds of skin that overlap the nail at its proximal and lateral edges. The proximal nail folds consist of ventral and dorsal portions. The ventral portion of the proximal fold adheres to the nail plate and cannot be seen externally.
nail matrix
The nail matrix is the specialized anatomical unit beneath the posterior nail fold to the distal edge of the lunula responsible for nail plate formation.
nail pitting
Punctate depressions in the nail plate.
nail plate
The hard, fully keratinized structure commonly referred to as the nail.
nail unit
An anatomic location or unit consisting of the nail plate, nail bed, nail folds, and nail matrix.
necrotic
Pertaining to the death of tissue in response to disease or injury.
nodose
Nodular.
nodule
A dermal or subcutaneous firm, well-defined lesion usually greater than .5 cm in diameter.

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nuchal
Pertaining to the nape of the neck.
nummular
Round to oval shape usually less than 2-3 cm in diameter. Coin-shaped.