Superimposed linear atopic dermatitis.

Superimposed linear atopic dermatitis is rarely manifested in polygenic disease as a counterpart to type 2 segmental mosaicism of monogenic skin diseases. Linear arrangement following Blaschko lines represents more severe disease on a generalized background of atopic dermatitis, perhaps reflecting clonal loss of heterozygosity. Only three cases of superimposed linear atopic dermatitis have been reported; we describe three additional cases.