Merck Manuals states that nail disorders come in many forms and may be caused by a variety of sources, including infections, injuries, internal diseases, structural problems, birth deformities, drugs and tumors. Depending on the physical signs, the Mayo Clinic stresses the importance of seeking medical attention.
Yellow-nail syndrome can be a sign of respiratory disease or lymphedema, the swelling of the hands. Other disorders include nail pitting, often related to psoriosis or a connective tissue disorders; nail clubbing, related to lung diseases; spoon nails, generally caused by an iron deficiency; Terry's nails, which can be a sign of aging, but may also be a sign of liver disease, congestive heart failure or diabetes; Beau's lines, which are connected to uncontrolled diabetes and peripheral vascular disease, as well as illnesses associated with a high fever; and onycholysis, associated with injury or infection. All these conditions, the Mayo Clinic shares, raise concern for underlying health conditions.