Tetrasomy 3q26.32-q29 due to a supernumerary marker chromosome in a child with pigmentary mosaicism of Ito

Pigmentary mosaicism of Ito (PMI) is a skin abnormality often characterized by hypopigmentation of skin, following, in most cases, the Blaschko lines, usually associated with extracutaneous abnormalities, especially abnormalities of the central nervous system (CNS). It is suggested that this pattern arises from the presence and migration of two cell lineages in the ectoderm layer during the embryonic period and embryonic cell migration, with different gene expression profiles associated with pigmentation. Several types of chromosomal aberrations, with or without mosaicism, have been associated with this disorder. This study comprised clinical description and cytogenetic analysis of a child with PMI. The G-banded karyotype analysis revealed a supernumerary marker chromosome in 76% of the analyzed metaphases from peripheral blood lymphocytes. Array genomic hybridization analysis showed a copy number gain between 3q26.32-3q29, of approximately 20.5 Mb. Karyotype was defined as 47,XX,+mar[38]/46,XX[12].arr 3q26.32-3q29(177,682,859- 198,043,720)x4 dn. Genes mapped in the overlapping region among this patient and three other cases described prior to this study were listed and their possible involvement on PMI pathogenesis is discussed.