Discussion :
Half and half nail also known as Lindsay’s nail was first described by
Lindsay in 1967 (1). Clinically, it shows as a nail with white proximal
portion and reddish brown or pink distal portion, with a sharp
demarcation line between the two portions, which usually remains
parallel to the distal free margin of the nail. It is a rare clinical
finding, but it can be frequently seen in chronic renal failure. It can
also appear in yellow nails syndrome, Crohn’s disease, Kawasaki’s
disease, Behcet’s disease, cirrhosis, hyperthyroidism, zinc deficiency,
citrullinemia, pellagra and HIV infection (2).
During the COVID-19 pandemic, several cutaneous manifestations have been
reported. Recently ; nail changes started getting attention, beginning
with transverse leukonychia (Mees lines) (3) ; to red half-moon nail
sign (4) and Beau lines (5). These nail alterations can be explained by
keratinization anomalies of nail tablet associated to vascularization
alterations of nail bed. A transient matrix injury caused by COVID-19
infection is suggested.