Mees’ lines

Mees’ lines (also called Aldrich–Mees lines) are transverse white bands that appear across the fingernails or toenails as a sign of certain systemic illnesses or toxic exposures.

What Mees’ lines look like
They are white, non-blanching horizontal bands running across the nail plate.
The lines move outward toward the nail tip as the nail grows.
They are usually present on multiple nails rather than just one.

Why they occur (Causes)Mees’ lines typically appear when something temporarily disrupts nail matrix (nail-forming tissue) activity.

Most common causes:
Arsenic poisoning – classical and most widely known cause.
Thallium poisoning.
Systemic infections – e.g., severe illnesses like:
Malaria
Pneumonia
Tuberculosis
Kidney failure / chronic renal disease.
Chemotherapy or other drugs that suppress cell division.
Severe stress to the body – major surgery, shock, or critical illness.

How Mees’ lines differ from Beau’s lines
Mees’ lines = white discoloration (a pigment/opacity change) in the nail plate.
Beau’s lines = grooves or depressions (structural change) in the nail.

Key Characteristics
Not painful.
Not caused by trauma to the nail.
Usually appear weeks after the triggering event.
Serve as a clue to past systemic illness or toxic exposure.

Medical significance
Finding Mees’ lines prompts healthcare providers to look for possible toxins, metabolic disorders, or severe prior illnesses. They are not a disease by themselves but a clinical sign.