Circumscribed, congenital and persistent alopecia of the scalp.

Abstract

At birth or in the first weeks of life, hair may lack within a more or less large but always circumscribed area of the scalp and this sign indefinitely per­sists throughout life. The four diseases which can be responsi­ble for this sign are, in decreasing order of frequency, sebaceous nevus, triangular alope­cia, aplasia cutis and pseudopelade associat­ed with some genetic disorders, above all in­continentia pigmenti. Let us define these four different con­ditions. (...).