Another observation of microphthalmia in an XX male: microphthalmia with linear skin defects syndrome without linear skin lesions.

A case of microphthalmia with Xp microdeletion is reported. The patient was a boy who showed bilateral microphthalmia with corneal opacities, hypospadias without evidence of hypogonadism, and a conduction disturbance of the heart (Wenckebach conduction). No skin lesion was discerned. High-resolution chromosome analysis revealed the karyotype of 46,X,del(X)(p22). The phenotype was considered to be microphthalmia with linear skin defects (MLS) syndrome without skin lesions. Polymerase chain reaction and fluorescence in-situ hybridization analyses revealed that the chromosome aberration resulted from an X;Y translocation: the presence of pseudoautosomal boundary Y and the sex-determining region of Y was confirmed, while Xp deletion involving the region distal to DXS1129 was ascertained. Thus the chromosome designation using the ISCN 1995 nomenclature is 46,X,der(X),t(X;Y)(p22.13;q11.2). Despite the absence of skin lesions, the Xp deletion of our patient corresponded to those of previously reported typical cases of MLS syndrome. Our observation further supports the current hypothesis that the phenotypic variation of MLS syndrome represents tissue-different X inactivation rather than different genetic effects of two contiguous genes.