Many conditions and diseases can show up in your fingernails. “Pitting, different-colored lines, visible ridges or spots on your fingernails, or nails that become brittle and break easily can be red flags,” says Beth Kassanoff, M.D., an internist at Baylor University Medical Center at Dallas. Here are some signs to look for.
One or more fingernails may start to curve downward and appear detached from the nail bed; your fingertips may also become enlarged. Nail clubbing is most often associated with lung disease, but it may also signal cardiovascular disease, liver disease, inflammatory bowel disease, or human immunodeficiency virus (HIV). Clubbing may also be hereditary.
Nails that are concave or thin and flat are associated with iron deficiency and anemia, but they’re more often caused by trauma or chemical exposure. Chemotherapy also may cause spoon nail, or koilonychia.
These depressions are known as Beau’s lines, named after the specialist who first identified the abnormality—as are many other nail disorders. Beau’s lines can occur as a result of an injury or trauma to the nail or nail bed, or an illness, condition, or treatment that affects the overall body, such as severe infection, malnutrition, or chemotherapy. The lines can also appear if you have peripheral vascular disease (a blood vessel disease that affects the limbs), uncontrolled diabetes, or a zinc deficiency.
Double white lines
Also referred to as Muehrcke’s nails, these double white lines run horizontally across the length of the nails and are sometimes associated with liver or kidney disease. They may occur after chemotherapy, as well.
White nail plates with a darker band of color at the top may indicate a condition called Terry’s nails. While normal aging is a possible culprit, dark bands can also be a sign of a serious illness, such as liver disease (cirrhosis), congestive heart failure, diabetes, or HIV.
Onychoschizia, or brittle nails, may sometimes, but rarely, be an indication of excessive vitamin A intake or conditions such as thyroid disease or osteoporosis (brittle bones). You may also find your nails breaking and splitting easily from too-frequent manicures, aging, or regular exposure of nails to water or chemicals, common among people with such occupations as dishwashers, housekeepers, or hairstylists.
Nail pitting, characterized by small depressions (“pits”) in the nail surface, is most often associated with nail psoriasis. The condition is also linked to skin dermatitis and certain connective tissue disorders such as reactive arthritis (once known as Reiter’s syndrome), sarcoidosis (an inflammatory disease), and alopecia areata (which causes hair loss).
Red, pink, or brown horizontal stripes
Known as half-and-half nails, apparent leukonychia, or Lindsay’s nails, these stripes can appear on up to 60 percent of the nail and be accompanied by dull, grainy white areas. Such nail changes can signal poor kidney function, such as chronic kidney failure and uremia (when waste products build up in the blood).