Pathogenesis of the Spooning

Abstract

Fourteen patients with koilonychia were reported. Four patients were with iron deficiency anemia and the other ten patients were occupationally induced cases. It is reported that koilonychia is related to various causative factors and diseases in the literatures. However, the pathogenesis of spooning has never been explained. I proposed a hypothesis as to the pathogenesis of spooning on the anatomical basis of the fingertip. Koilonychia is frequently found and severely affected in the thumb, index and middle fingernails. It seems that the frequency and severity are related to the pressure-bearing function of the fingers in the handiwork. The ungual pyalanx is only the heart of the distal portion of the finger. Therefore, the distal and lateral portion of the nail plate are directly affected by the upward pressure by reason of the absence of the ungual phalanx. This may be demonstrated by pressing the tips of one�s fingers on to a table top and observing the reddening and whitening of the nail bed. The nail plate and the ungual phalanx bear the force which act on the palmar aspect of the fingertips. The upward force is larger than the holding down force of nail plate in the absence of ungual phalanx, upward pressure forces causing upward deformation of distal and lateral portion of the nail plate. So the nails become gradually flat and eventually concave with the edges everted. As a logical conclusion, the thin nails in iron deficiency anemia are prone to concave easily by the weak force. © 1985, Meeting of Osaka Dermatological Association. All rights reserved.