Female pattern hair loss: beyond an androgenic aetiology?

ting phenomenon. Twin spotting was described as two different recessive mutations occurring on either pair of homologous chromosomes, followed by mitotic cross-over leading to formation of two different homozygous daughter cells that form the stem cells of two different mutant lesions. Twin spotting arises from allelic or nonallelic mutations. Dichotomic functional abnormalities of the same tissue such as vascular twin naevi (naevus telangiectaticus and naevus anaemicus) or melanotic and achromic twin naevi suggest allelic mutations. On the other hand, unusual paired mutant skin lesions such as phacomatosis pigmentovascularis or phacomatosis pigmentokeratotica are most likely the result of nonallelic mutations. We therefore believe that the coexistence of lentiginosis within lesions of LAM in the present case might be regarded as a novel example of nonallelic twin spotting. However, the possibility of an arbitrary coincidence cannot be fully ruled out. In conclusion, this was a unique case with extensive involvement of LAM colocalized with segmental and spotty lentiginosis suggesting a novel example of twin spotting. With an increasing number of reported cases, we hope that a wider spectrum of associated conditions would come to attention that might help to elucidate the genetic background of the disorder.