Bumpy ridges on the fingernails can be caused by aging, nail injury, lack of moisture or poor nutrition, according to Dr. Phoebe Rich, M.D., clinical adjunct professor of dermatology at Oregon Health Science University. Aging is the most common cause of bumpy fingernails.
There are two main types of bumpy nails: those with vertical ridges and those with horizontal ridges. Lengthwise ridges are more common, tend to be less serious and are like wrinkles in the nails that get more pronounced with age, says Rich. In rare cases, vertical ridges may be caused by certain diseases such as rheumatoid arthritis. If the vertical ridges appear suddenly, they could signify the presence of a rare condition called lichen planus, which also often causes skin rash.
Horizontal nail ridges are more likely to indicate a serious underlying health condition, according to Mayo Clinic. These indentations, called Beau's lines, are associated with peripheral vascular disease, uncontrolled diabetes, pneumonia, measles, mumps and scarlet fever. Beau's lines can also be a sign of a severe zinc deficiency.
If a singular horizontal ridge appears, it may be sign that nail growth was temporarily disrupted while the body was fighting off illness, explains the Huffington Post. However, if nail defects keep occurring as the nail grows out, it signifies an ongoing problem with nail growth, which can occur with kidney, lung or liver disease, states Jessica Krant, M.D. Recurring ridges may also be accompanied by nail discoloration, such as whitening or yellowing.