Epidermal naevus

Epidermal naevi (are developmental anomalies that follow the lines of Blaschko. Although often present at birth, they may appear later in childhood. Small ones consist of single or multiple parallel linear grey-brown warty plaques. Larger ones are linear on the limbs but tend to follow a predictable swirling pattern on the trunk. At times they are quite inflammatory (ILVEN or Inflammatory Linear Verrucous Epidermal Naevus). Incontinentia pigmenti and hypomelanosis of Ito are other less common ‘birthmarks’ that follow a similar linear and swirled arrangement. They are believed to be due to somatic mosaicism, but the exact mechanism has not yet been worked out.