Red Lunulae May Signal Underlying Health Conditions

Health conditions that are not immediately apparent can sometimes reveal themselves through related physical changes that emerge before clear symptoms develop.

Such changes can serve as useful warning signs, prompting scans and helping clinicians begin appropriate treatment.

Red lunulae and underlying health conditions

A review of case reports in the American Journal of the Medical Sciences, conducted by researchers at Rutgers New Jersey Medical School, has outlined the association between reddish lunulae - the half-moon areas at the base of the fingernails - and numerous conditions. These include heart failure, liver cirrhosis and rheumatoid arthritis.

Lunulae seldom change from their usual white colour to red. When they do, however, the change is often connected with an undisclosed health problem elsewhere in the body, although the researchers say the reason for this link is not yet fully understood.

The review recommends comprehensive health assessments for people who show red lunulae, in order to establish whether another condition could be present.

"First described in 1954, numerous other cases have since been delineated and an association with cardiovascular, hepatic, hematologic, dermatologic, and rheumatologic disorders has been apparent," write the researchers in their published paper.

"Though the precise etiology remains unclear, red lunulae may reflect both systemic disease activity or local pathology such as subungual tumors."

What nail lunulae do

The lunula produces new cells containing keratin, the protein that is pushed forwards and hardens to form the remainder of the nail. Lunulae are generally easier to see on the thumbs and big toes.

Although red lunulae have been associated with heart disease and other conditions for many decades, this review is the broadest assessment of reported cases so far.

One of the newer studies considered by the team linked these discoloured areas of the nail with connective-tissue diseases. Yet red lunulae do not occur in every person with these diseases, and not everybody with red lunulae is found to have an underlying condition.

Case reports have also documented red lunulae in people with alopecia areata and carbon monoxide poisoning. The researchers found that cardiovascular, autoimmune and rheumatologic conditions appeared most frequently in the available literature.

When red lunulae may need investigation

The review states that systemic disease is more likely if the red colour appears on several nails rather than a single nail.

When only one nail is discoloured, an issue beneath the nail - known as a subungual problem - is generally more likely.

"If further examination reveals the presence of red lunula on a single nail along with a nail bed infection, subungual tumor, subungual hemorrhage, or red discoloration of the entire nail plate or that exceeding the borders of the lunula, the clinical diagnosis of red lunula should probably not be rendered," write the researchers.

A future avenue of research may be to examine the biological processes that connect these reddened nail areas with the various health conditions. Capillary vasodilation appears to be involved: this is the widening of the tiny blood vessels beneath the nail, which increases blood flow.

The review also describes a test clinicians can use. If pressing on a red lunula makes it become white, capillary vasodilation may be responsible, indicating an issue in the vascular system that requires attention.

A lunula can take on several different colours. Blue, for example, may indicate diabetes, while brown is associated with kidney disease. The central message of this review, however, is that red discolouration should not be disregarded if it appears.

These frequently overlooked parts of the nails can offer valuable clues about the body's health.

"Given the rarity of the occurrence, its potential diagnostic relevance is often overlooked," write the researchers.

"When identifying red lunulae, clinicians should consider connections to underlying systemic or dermatologic disease. This subtle clinical sign may facilitate early detection and identification of salient systemic disease."

The research was published in the American Journal of the Medical Sciences.

This article was fact-checked and edited by Fiona MacDonald. Although we take pride in our process, we are only human. If you notice an error, please let us know.