According to Dr. Standley, flat nails can indicate Raynaud's Disease, a condition characterized by cold fingers and toes. Flat nails can also be caused by an iron, protein or vitamin B12 deficiency, psoriasis or diabetes.
Nails change for a variety of reasons. According to WebMD, the most common cause of changes in texture or color is fingernail fungus, which can also cause nails to crack and peel. Irregular growth, pitting, dark brown streaks or warts may all indicate a more serious condition. Changes in the nail typically result from nutritional deficiencies or specific diseases. However, WebMD challenges the belief that these changes are early indicators of disease, with the American College of Physicians pointing out that other symptoms are more likely to manifest first. In addition, not all patients are equally likely to show changes in their nails. According to Huffington Post, while minor and occasional changes are not cause for concern, persistent abnormalities and defects that keep occurring as the nail forms indicate an ongoing problem that is more likely to stem from a disease.
To improve nail appearance, WebMD advises moisturizing the nails and cuticles frequently and avoiding trimming the cuticles too closely, minimizing the risk of infection.