Onychorrhexis refers to alternating longitudinal thickening and thinning, or ridging, of the nail plate. Longitudinal splitting may also occur. The first fingernails are most commonly affected. Onychorrhexis is believed to be a result of disordered keratinization in the nail matrix and is due to a variety of conditions:

• Normal aging
• Physical factors: repetitive trauma, frequent soap and water exposure, manicures and pedicures, tumors compressing the nail matrix
• Chemical factors: use of nail polish removers, cuticle softeners, and nail cosmetics
• Systemic disease: hypothyroidism, malnutrition, and eating disorders (eg, anorexia nervosa, bulimia)
• Dermatologic disease: psoriasis, lichen planus, lichen striatus, Darier disease, atopic dermatitis, pityriasis rubra pilaris, brittle nail syndrome, alopecia areata, chronic graft-versus-host disease, pemphigus vulgaris, and ectodermal dysplasia
• Medication use: oral retinoid therapy, topical antifungal nail lacquer application