Iron deficiency has been discussed as an etiologic factor in diffuse alopecia. Although the mechanism of alopecia related to iron deficiency remains unknown, the diagnosis is confirmed if hair loss ceases with iron administration. However, hair structure abnormalities due to iron deficiency are less known. We report a case of hair structure abnormality associated with iron deficiency anaemia. The hair structure abnormality was a fusiform and expanded node of the hair shaft. The hair loss ceased and the abnormality was corrected with iron administration.