Nails in light and electron microscopy.

The study and the diagnosis of nail disorders benefit from examination under light and electron microscopes. The alterations occurring in the matrix, bed, and hyponychium are comparable to those observed in the skin. Architectural and cellular alterations--loss of the cell's regular alignment, changes in stain affinity, parakeratosis, and changes in the intercellular spaces--are observed in the nail plate and subungual keratin. The intensity and singularities of these lesions are usually sufficient to orient the diagnosis from examination of the keratin alone. This microscopic examination is of particular interest in dealing with mycoses because it can specify the type of invasion of the keratin and avoid false-positive or false-negative results on culturing. Electron microscopy allows easy differentiation of melanin and ferric pigments.