What is Onychodystrophy?

Onychodystrophy is a term that describes malformation of a fingernail or toenail. In medical terms, the word is often used in reference to a congenital condition that causes abnormalities in finger bones, leading to malformation of fingernails. Onychodystrophy also can be caused by a wide variety of infectious and noninfectious diseases.

Nails are made up of cells that are cornified, which means they have produced large amounts of a durable, fibrous protein called keratin. In addition, cornified cells no longer undergo any metabolic processes and essentially are dead cells. The nail lies on top of, and is attached to, the nail bed, which is made up of cells that metabolize and divide very slowly. Deformities of the nail are often caused by infection of the nail bed or deformity in underlying bone.

Onychodystrophy is a very wide-ranging term, because it refers to any abnormal change in the nail, excluding changes in color. The term therefore can refer to changes in nail shape, size, strength and brittleness, infections of the nail bed and infections of the tissue surrounding the nail. These can be caused by diseases such as dermatitis, fungal or bacterial infections, inflammatory diseases and even tumors. In addition, nail abnormalities can be caused by certain medications, such as anti-malarial and antiviral drugs and antibiotics, and by recreational drug use.

This term most often refers to any abnormal nail change, but it also can be used in a more specific manner. Congenital onychodystrophy of the index fingers (COIF) is a syndrome in which abnormalities of the finger bones cause dysplasia of the index finger nails. The affected nails can be deformed in one of several ways. For example, the nails might be smaller than normal for the size of the finger, or there might be multiple small nails on the nail bed instead of one large nail. In some cases, the nail might be absent altogether.

The cause of this condition is not well understood. Although it generally is believed that the condition is genetically inherited, there is some evidence that many cases are of spontaneous origin. In cases where there is no family history of the condition, it is believed that an in utero ischemic injury might be the cause. An ischemic injury is one that is caused by a lack of blood and oxygen being supplied to the affected area. In this case, the nail abnormality might be because of reduced blood supply to the fingers during fetal development.

Treatment for onychodystrophy depends on the underlying cause of the condition. Often, the nail abnormality itself does not require treatment; instead, the disease causing the abnormality is treated. When the nail abnormality is caused by COIF, no treatment is necessary unless an individual with the condition chooses to undergo surgery for cosmetic reasons.