Linear atrophoderma of Moulin: postulation of mosaicism for a predisposing gene.

Hyperpigmented atrophoderma arranged in a pattern following the lines of Blaschko and appearing during childhood or adolescence on the trunk or the limbs is a characteristic feature of linear atrophoderma of Moulin. We review 15 published reports and describe 4 additional cases. Histopathologically, there is no clear sign of atrophy found in specimens examined by light microscopy. It might well be argued that a focal reduction of subcutaneous fatty tissue contributes to the obvious clinical atrophy. The cause and pathogenesis of the disorder remains unknown. It may reflect mosaicism caused by a postzygotic mutation that occurred at an early developmental stage, in analogy to many other diseases distributed along Blaschko's lines. Linear atrophoderma of Moulin may reflect the action of an autosomal lethal gene surviving by mosaicism. There are so far no reports of a familial occurrence that could favor a paradominant transmission of linear atrophoderma of Moulin. However, theoretically, the postzygotic mutation giving rise to an aberrant cell clone could still be nonlethal. In a heterozygous individual, a postzygotic mutational event might lead to loss of the corresponding wild-type allele at the atrophoderma locus. This would give rise to a homozygous cell clone, which becomes manifest along the lines of Blaschko later in life.