Beau’s lines

These are grooved horizontal lines running on either the fingernails or toenails. They can look like ridges. They happen due to a temporary cessation of nail matrix cell division and are a non-specific finding.

Chemotherapy can cause this, but there are also a number of other causes (infection, trauma, malnutrition, hypocalcaemia). They can also be seen a couple of months into Kawasaki disease.