Pathogenesis of onychoschizia (lamellar dystrophy).

Onychoschizia or lamellar dystrophy of the nails is common, especially in adult women, but little information is available about its cause. Most theories involve environmental factors, but supportive experimental data are scarce. Therefore we studied the in vitro nail changes produced by several organic solvents, detergents, water, other polar materials, and both acidic and basic solutions. Challenged and control fingernail clippings were examined grossly, microscopically, and by scanning electron microscopy at regular intervals. There was a progressive increase in severity with prolonged wetting and drying. By 3 weeks, scanning electron microscopy demonstrated unattached individual cells in empty spaces in which separation was more prominent. Basic solutions caused some softening, but layering (peeling) was seen only after repeated hydration and dehydration. Although other factors may influence onychoschizia, the typical changes can be produced in normal nails after a 21-day challenge of repeated exposure to water followed by dehydration. These findings suggest a probable cause for the condition and a logical approach to management.