Curved fingernails are often a symptom of an underlying medical condition, such as anemia or an iron deficiency, according to WebMD. Curved fingernails may also indicate a symptom of diseases, such as chronic obstructive pulmonary disease, emphysema or interstitial lung disease.
In less severe cases, curved fingernails may also indicate the nails have grown too long. Curved fingernails typically alert physicians to lung and pulmonary conditions, explains WebMD. Chronic obstructive pulmonary disease is a chronic lung disease where an obstruction makes breathing difficult, whereas emphysema, also a chronic lung disease, causes chronic coughing, wheezing and shortness of breath. Interstitial lung disease consists of a group of lung disorders that causes a dry cough and shortness of breath, as well as curved fingernails.