WE HAVE recently observed three cases of a unique idiopathic distortion in the shape of the nails in which there appears to be an excessive transverse curvature of the nail plate, thus producing a pinching and loss of soft tissue of the involved fingers. This nail dystrophy may produce severe pain in the involved digit and relief can be achieved by removal of the plate. Report of Cases Case 1. —In August 1959, a 54-year-old white woman was seen as an outpatient at the Hospital of the University of Pennsylvania for pain of one month's duration in the distal portion of the right thumb. The patient stated that there had been a gradual onset of pain without apparent cause. There had been no unusual trauma and the patient knew of no foreign body entering the skin. On examination, all nails of both hands and feet showed an unusual degree of