Mosaic tetrasomy 13q in the differential diagnosis of hypomelanosis of Ito.

Abstract

Hypomelanosis of Ito is one of cutaneous patterns of pigmentary mosaicism characterized by regions of skin hypo- and hyperpigmentation and associated with mosaic numerical and structural chromosomal abnormalities. A comprehensive cytogenetic and molecular cytogenetic analysis was conducted on cells derived from two tissues of seven patients initially diagnosed with «Hypomelanosis of Ito». In two of these patients, mosaic segmental tetrasomy involving the distal region of the q-arm of chromosome 13 was identified. This chromosomal abnormality is not typically associated with hypomelanosis of Ito but is instead linked to another form of pigmentary mosaicism, known as phylloid hypomelanosis. These findings underscore the importance of employing cytogenetic and molecular cytogenetic techniques as a critical component in the differential diagnosis of various forms of pigmentary mosaicism.