Pigmentary abnormalities in trisomy of chromosome 13.

This paper documents an unusual pigmentary mosaicism in a patient with translocation trisomy of chromosome 13. The dermatological lesions include: (1) broad hypopigmented bands following the typical description of Blaschko's lines on the dorsal aspect of both lower limbs; (2) horizontal linear streaks over the spine without the typical central V-shaped dip of Blaschko; and (3) a 'patchwork' hypopigmentation over the face, neck, chest, upper limbs and ventral surface of lower limbs. The lesions in (3) resemble the rare 'phylloid' or leaf-like pigmentary mosaicism type 3 of Happle, but differ in that the pattern shows no midline separation. A translocation trisomy 13 was uniformly detected on peripheral lymphocyte and skin fibroblast cultures from the hypopigmented and normal skin and there was no evidence of cytogenetic mosaicism or chimerism. These lesions resemble those of hypomelanosis of Ito on histopathological assessment.