Dented fingernails are usually caused by an underlying health conditions, such as psoriasis, eczema, alopecia areata and Reiter Syndrome. These diseases affect the growth of the nail in the nail matrix or cause a loss of some cells.
Nail imperfections such as dents or pits can have a number of causes. However, the way the nail is damaged can help indicate the problem. Horizontal dents that appear at the base of the nail and grow outwards occur when something stops the nail growth. When the growth starts up again, the nail appears to have a horizontal dent. Possible causes include vitamin deficiency, trauma to the nail bed, psoriasis, alopecia areata, and Reiter Syndrome, as stated by MedGuidance .
Nail pitting often appears as small pin prick, or circular dents in the nail. There may only be one or two or a large number of these dents. The cause is a loss of parakeratotic cells in the nail plate, as stated by DermNet NZ. Health conditions indicative of this particular type of denting are psoriasis, eczema, reactive arthritis and alopecia areata.
Some health conditions can produce two or more types of nail imperfections, such as psoriasis. The appearance of minor imperfections is not usually something to worry about. However, more serious or chronic nail pitting and dents should be examined by a doctor.