Congenital hypotrichosis due to short anagen.

Two children with congenital hypotrichosis are described. Both presented with persistent short, fine hair since birth. Evidence is provided that the short hair observed in these patients is due to a short anagen phase of the hair cycle, with a normal rate of hair growth. Shortening of the anagen phase of the scalp hair cycle leads to a decrease in the maximal hair length and an increase in the number of hairs in telogen, resulting in an increase in hair shedding. Scanning electron microscopy showed a widely spaced cuticular pattern, a finding typically seen in hair of thin calibre. One patient had affected family members with an apparently autosomal dominant mode of inheritance. The disorder appears to resolve spontaneously during puberty and adulthood.