What is Linear and whorled nevoid hypermelanosis?

Linear and whorled nevoid hypermelanosis is a disorder of pigmentation that develops within a few weeks of birth and progresses for one to two years before stabilizing. There is linear and whorled hyperpigmentation following the lines of Blaschko without preceding bullae or verrucous lesions. It is important to exclude other pigmentary disorders following the Blaschko lines before making a diagnosis of linear and whorled nevoid hypermelanosis. The differential diagnoses include incontinentia pigmenti, linear epidermal nevus, hypomelanosis of Ito and Goltz syndrome. Recently, a case of linear and whorled nevoid hypermelanosis was reported in a Malaysian Chinese girl.