Mees’ lines are distinctive visual markers appearing on fingernails and toenails, characterized by white discoloration. These lines are a type of transverse leukonychia, a white discoloration extending across the nail plate. Mees’ lines are not a disease themselves; instead, they serve as a symptom indicating a past systemic event or medical condition that temporarily disrupted normal nail growth. Their presence suggests a significant physiological stressor or exposure impacted the nail matrix.
Identifying Mees Lines
Mees’ lines manifest as single or multiple white, transverse bands stretching across the entire width of the nail plate. These lines run parallel to the cuticle and the white tip of the nail. Unlike other nail discolorations, Mees’ lines do not disappear or blanch when pressure is applied. They are smooth and do not present with any palpable ridges or changes in the nail’s texture.
As the nail grows, these lines gradually move outward from the cuticle towards the free edge. This outward movement is significant because the line’s position can help estimate when the causative event occurred. Mees’ lines can appear on one nail or all nails simultaneously, affecting both fingernails and toenails, though they may be less distinct on toes.
Underlying Causes
The appearance of Mees’ lines often signals systemic poisoning or considerable physiological stress. Historically, these lines have been most famously linked to arsenic poisoning, which can cause multiple horizontal white bands across the nails. Other heavy metal toxicities, such as thallium and lead poisoning, are also recognized causes.
In modern contexts, chemotherapy drugs are a common cause of Mees’ lines due to their impact on rapidly dividing cells, including those in the nail matrix. Severe systemic illnesses can also disrupt overall body function and lead to these nail changes, including kidney failure, heart failure, and liver disease. Severe infections like pneumonia, malaria, measles, or tuberculosis, as well as acute medical events, can also induce their formation. The presence of these lines warrants a medical evaluation to determine the underlying cause, as they can indicate serious health issues requiring prompt attention.
Significance and Resolution
While Mees’ lines themselves are not harmful, their significance lies in pointing to a past medical event or exposure. They serve as a visible record of a temporary disruption in nail growth. Identifying the lines often begins with a visual inspection by a healthcare provider. This is followed by a detailed patient history to uncover potential exposures or recent illnesses. To pinpoint the underlying cause, a doctor may order various tests, including blood or urine analyses, especially if heavy metal poisoning is suspected.
Mees’ lines do not disappear once they form; rather, they grow out with the nail over several months as the nail plate regenerates. The time it takes for them to grow out can help estimate when the causative event occurred, as fingernails grow approximately 3 millimeters per month. Treatment focuses on managing the underlying condition or eliminating the exposure that caused the lines. Once the root cause is addressed, no new lines will form, and existing ones will eventually be trimmed away as the nail grows.