Robert Shmerling, M.D., is associate physician and clinical chief of rheumatology at Beth Israel Deaconess Medical Center and an associate professor in medicine at Harvard Medical School. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program and has been a practicing rheumatologist for over 25 years.
Are there any diseases that can be diagnosed by disorders of the fingernail and toenails?
In general, looking at the fingernails and toenails is not a reliable way to tell if you are healthy or not. But a careful examination of the nails can provide clues to certain diseases.
Here are some examples:
Fungal infectionToenail 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 diseaseConditions 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.
AnemiaPeople 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.
Serious illnesses of almost any type can affect the appearance and growth of the nails. Your doctor may be able to tell if you were sick up to several months ago by the appearance of a horizontal ridge or indentation in finger nails, called Beau's lines. These lines may occur after any serious illness, including those associated with a high fever or severe nutritional deficiency. They may also appear soon after getting chemotherapy for cancer.
So, there are situations when the nails offer a glimpse into your health. But, most of the time, there are better ways.