Type 2 segmental Darier disease

A 45-year-old man had bilateral disseminated involvement of Darier disease, and two of his sisters likewise had lesions suggesting this trait. Remarka bly the propositus showed, in addition, a unilateral, systematized, segment al pattern of excessively pronounced Darier lesions. This unusual case can be taken as an example of type 2 segmental Darier disease. In contrast to t he type 1 segmental manifestation that develops from a new mutation occurri ng in an otherwise healthy embryo, the type 2 segmental involvement would o riginate in a heterozygous embryo from postzygotic loss of the correspondin g normal allele, resulting in a cell clone that is either homozygous or hem izygous for the mutation. This concept would explain why the segmental lesi ons were excessively pronounced and superimposed on the ordinary trait. Fut ure studies may show whether the concept of type 2 segmental Darier disease can be confirmed at the molecular level.