A transverse band in a nail is caused by a temporary alteration in the normal production of nail substance as it is produced by the nail matrix that underlies the proximal nail fold.1 A fingernail band that is concave distally is usually caused by the trauma of manicuring, the nail being temporarily damaged by the instrument as it pushes back and follows the curve of the proximal nail fold. A distally convex band is generally caused by a temporary abnormality of the skin of the dorsum of the terminal phalanx. Contact or parasitic dermatitis of a digit will produce this in one nail; systemic disease, such as lobar pneumonia, is capable of producing transverse bands in the nails of both the hands and the feet. When a patient has distally convex, transverse bands only of all nails of the hands, the conditions leading to the abnormality are uncommon. Pigmentation