One of my customers has a split down the center of her thumbnail that starts at the matrix and grows out with the nail. The condition appeared about three months ago and is on both of her thumbnails. Sometimes she has it, sometimes she doesn’t.
Your client appears to have a median nail deformity. Because the split comes and goes, it is unlikely that her condition is caused by a serious underlying disorder – infections and tumors do not come and go. Additionally, median deformities almost always occur on the thumbs.
What is a median nail deformity? It is a change in the nail plate that is produced by a nervous habit. The individual unconsciously presses down on the cuticle of her thumb with the adjacent index finger. Repeated pressure on the soft nail forming underneath the cuticle and proximal nail fold causes a longitudinal indentation down the center of the nail plate. With enough repeated pressure, the nail will split down the middle.
Correcting the deformity isn’t as easy as diagnosing it. Your client must break her habit and resist the urge to press on one nail with another finger. When the pressure stops, the deformity will resolve and the nail will return to normal within four to six months.
By identifying the cause and cure of your client’s condition, you will ensure the client’s respect and gratitude toward you. --Paul Kechijian, M.D.