Here are some examples:
- Fungal infection: Toenail fungal infections affect up to 5% of the population. For most people, the condition is primarily cosmetic. Treatment is optional. But if an infection is painful or occurs in a person with diabetes, treatment may be offered.
- Lung disease: Conditions such as lung cancer, lung scarring (pulmonary fibrosis) and cystic fibrosis may be associated with clubbing of the fingernails. With clubbing, the nails take on a raised, rounded appearance, like a club. But it's not completely reliable: many people with lung disease do not have clubbing and healthy people sometimes have clubbing, too.
- Psoriasis: "Pitting" (small indentations) in the nails and thickening of the nails are common in people who have psoriasis. In fact, these nail changes may be the first or only sign of this condition.
- Endocarditis (a heart valve infection): A heart valve infection is a serious condition, and can be hard to diagnose. Fever, shaking chills and rash are common symptoms. The appearance of multiple red lines under the nails — called "splinter hemorrhages" — may suggest the diagnosis.
- Anemia: People with anemia tend to have pale nail beds. However, it's usually difficult to say whether a nail bed is pale enough to indicate anemia. Blood tests are more reliable.
So, there are situations when the nails offer a glimpse into your health. But, most of the time, there are better ways.
Find out more about this book:Harvard Medical School Arthritis: Keeping your joints healthy