The spontaneous separation of the nail plate from the matrix area while the distal part of the nail plate is still firmly attached to the nail bed. The remaining nail plate is eventually shed. Associations include infections, drug reactions, radiation, pemphigus vulgaris, alopecia areata universalis, finger or wrist fracture with cast immobilization, reflex sympathetic dystrophy, yellow nail syndrome, keratosis punctata, acute paronychia, and repeated local trauma from footwear. Some cases are idiopathic. A rare familial form with autosomal dominant inheritance has been reported. When acute, may be associated with swelling of the proximal nail fold. The course is typically self-limited.