Vertical ridges that appear on the nail can indicate disorders as simple as iron deficiency, poor absorption of vitamins and nutrients, kidney disease or can be due to pterygium. Pterygium of the nail is scarring from the base of the nail outward in a V formation, which leads to loss of the nail.I suggest you to get an examination done from a dermatologist to confirm the diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I have the same nail problem(middle finger) looks exactly like your picture, I asked a doc. in 2005 and she didn't know(family doc.) Sure would like to know.