Nail Abnormalities at High Altitude

With summer just around the corner, more people will be hitting the mountains for some high altitude hikes and 14ers. There have been numerous anecdotal findings of mountaineers with changes to their fingernails after ascending the world’s tallest peaks, with the most common abnormalities being Mees’ lines, Muehrcke’s lines, and Beau’s lines. While the peaks in Colorado do not compare to those of the Himalayas, there is always a chance, albeit very low, that you may notice some changes to your nails after a high altitude expedition.

Both Mees’ lines and Muehrcke’s lines are types of leukonychia, which means “white nails”. Mees’ lines present as a single horizontal white band, sometimes multiple, located in the nail plate and are non-blanching. Throughout history, Mees’ lines have been associated with drug toxicity, such as from arsenic or thallium.4 Additionally, there are many systemic diseases that have been associated with Mees’ lines in which the body is experiencing high amounts of stress, such as with myocardial infarction, sickle cell crisis, and tuberculosis.4

Mee’s lines

One case report, “Mees’ lines in high altitude mountaineering”,  by Avinash Aujayeb details how a 27-year old man developed Mees’ lines after he traversed high altitudes in the Pakistani Karakorum range, attempting to scale a summit of 7031 meters.1 He acclimated to altitude at a camp located at 4000 meters,  and stayed for a total of 21 days. No medications were used for acclimatization. In his attempt to reach the summit, he became extremely fatigued and hypothermic, and turned around at 6900 meters. Upon return to sea level, he lost about 17 pounds of weight. Six weeks after his expedition, he developed non-blanching horizontal white lines on his nails, consistent with Mees’ lines. The lines eventually moved distally and completely disappeared. While the paper does not go on to hypothesize the cause of this man’s development of Mees’ lines, it seems reasonable that they appeared due to the stress the man endured as evidenced by his need to turn around early from fatigue and hypothermia, and likely hypoxia given the extreme altitude.

Muehrcke’s lines present as a pair of horizontal white bands located in the nailbed, the skin beneath the nail plate, making them blanchable (unlike Mee’s lines which are located within the nail itself). Muehrcke’s lines usually present on the 2nd, 3rd and 4th fingers, and typically spare the thumb. Historically, these lines are most associated with hypoalbuminemia as seen in a protein-losing condition of the kidney called nephrotic syndrome.4 They have also been found in disease states of systemic immunosuppression, such as in HIV, where the metabolism of the body is stressed and has decreased ability to make proteins. 4

Muehrcke’s lines

The discovery of Muehrcke’s lines was first published in the British Medical Journal in 1956 by Robert C. Muehrcke.4  In the paper, he details a study in which he compared 750 adult patients and healthy volunteers who had normal serum albumin against 65 patients known to have chronic hypoalbuminemia.  He saw that the pair of white horizontal lines were only in those with the chronic hypoalbuminemia, most specifically those with a serum albumin below 2.2 g/dL.4 Once these patients were treated and their albumin concentrations increased, the lines disappeared after a few weeks. He thought the findings suggested that Muehrcke’s lines were from an albumin deficiency due to poor nutrition.

In a letter to the editor of High Altitude Medicine and Biology, authors Windsor, Hart, and Rodway describe the presence of Muehrcke’s lines on Mount Everest after a 38 year old with no significant medical history noticed their appearance a few weeks after he had returned to sea level.3 There were two parallel horizontal lines under the nails of his 2nd, 3rd, 4th, and 5th digits, sparing the overlying nail. They believe the development of these nail findings were indeed from hypoalbuminemia , however do not believe it was from a nutritional deficiency as Muehrcke first described, because the climber had been healthy throughout his expedition and he maintained good nutrition.3 They attribute the findings to peripheral edema, which is a common finding in high altitude mountaineers. With this edema, fluid levels in the tissues increase. The authors believe this may have inhibited the growth of the nailbed, which then resumed with return to sea level.

Another nail finding from high altitude mountaineering is called Beau’s lines, which are an indented groove across the span of the nail horizontally, beginning at the base of the lunula. The lines result when nail formation is temporarily halted during episodes of stress, and usually present several weeks after the stressful incident.2 They are generally caused by local trauma to the nail, extreme temperatures, and toxicity from chemotherapy.4

Beau’s lines

There was a prospective study completed by authors Bellis and Nickol in High Altitude Medicine and Biology where the study participants were completing a research expedition in eastern Nepal in April and May of 2003.2 The maximum altitude reached varied from 5,142 to 6,476 meters and the length of stay of each individual also varied. The study found Beau’s lines developed in 1 out of 56 participants at 4 weeks, however by 8 weeks, 17 out of the 52 (or 33%) developed Beau’s lines. The authors hypothesized that the changes were possibly due to the hypoxic as well as hypobaric environment which could diminish the activity of the nail matrix. However, they did acknowledge the fact that there were other factors that could have resulted in the Beau’s lines, such as extreme cold conditions and possible injuries to the fingers due to the nature of the work of the researchers. No participants reported frostbite or any damage to the hand, however at night temperatures dropped as low as negative 20 degrees Celsius.

Clubbed fingers

These nail abnormaltities are less likely to be found during expeditions within the United States unless hiking in Alaska, which has Denali, the tallest peak in the US at 20,310 meters. Outside of Alaska, the tallest peak is Mount Whitney in California, which pales in comparison at 14,505 meters. Most of the case reports completed on these nail findings were from several week-long expeditions in the Himalayas. However, condition you may already be aware of is clubbing of the fingers. This presents as a bulbous enlargement of the fingertips caused by chronic hypoxia. During my five-week visit here, I have anecdotally heard from two different Summit County residents that they have many healthy and young friends with clubbed fingers. Unfortunately, I was unable to find any research on the prevalence of clubbed fingers among individuals living at high elevations, but I believe it is something that deserves to be looked into deeper. 


  1. Aujayeb, A. (2019). Mees’ lines in high altitude mountaineering. BMJ Case Reports, 12(3), 1. doi:10.1136/bcr-2019-229644
  • Bellis, F., & Nickol, A. (2005). Everest Nails: A prospective study on the incidence OF Beau’s lines after time spent at high altitude. High Altitude Medicine & Biology, 6(2), 178-180. doi:10.1089/ham.2005.6.178
  • Windsor, J. S., Hart, N., & Rodway, G. W. (2009). Muehrcke’s lines on Mt. Everest. High Altitude Medicine & Biology,10(1), 87-88. doi:10.1089/ham.2008.1079
  • Zaiac, M. N., & Walker, A. (2013). Nail abnormalities associated with systemic pathologies. Clinics in Dermatology,31(5), 627-649. doi:10.1016/j.clindermatol.2013.06.018

Makenna Schmidgall is a second-year physician assistant student at the Midwestern University Physician Assistant Program in Glendale, Arizona. She grew up in Gilbert, AZ, but left her desert home to attend New York University in the Big Apple where she earned a bachelor’s degree in Global Public Health/Biology. During her junior year of college, she began working as an ER scribe in multiple emergency departments of the Mount Sinai Health System in New York, NY. She enjoys gardening, hiking and playing with her new Labrador retriever puppy “Piper”.  

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