Everest nails: a prospective study on the incidence of Beau's lines after time spent at high altitude.

Beau's lines are transverse grooves seen in the nails that appear after a period of disruption in nail matrix formation. The fall in atmospheric pressure at high altitude causes hypobaric hypoxia in individuals spending time at high altitude, which may result in disruption of nail matrix formation and the appearance of Beau's lines. Members of an expedition to a research base camp at 5000 m in the Nepal Himalayas were contacted 4 and 8 weeks after returning to low altitude to report on the appearance of new transverse grooves in their nails. During the expedition, data on altitude, acute mountain sickness score, oxygen saturation, and the use of medications were collected by each individual in a twice-daily log book. Fifty-nine individuals consented to enroll in the study, with 52 (88%) contacted at follow-up at 8 weeks. The incidence of Beau's lines was 33%. There was no relationship to maximum altitude reached, minimum oxygen saturation, duration of various levels of hypoxia, worst AMS score, or length of stay above 4000 m (p = 0.118). The hypoxia associated with the hypobaric environment at high altitude could be sufficient to cause a disruption in nail matrix formation.