Phylloid Hypermelanosis: An Unusual Form of Pigmentary Mosaicism

Abstract

In this issue, Oiso et al. [1] present an unusual case of pigmentary mosaicism. A 29-year-old man with mental deficiency had hypermelanotic macules arranged in a phylloid pattern. Cytogenetic analysis of peripheral blood lymphocytes showed 3 different aberrant cell types containing either a monocentric or a dicentric ring chromosome 13, or monosomy 13. Remarkably, no normal karyotype could be found in the 30 cells examined. Although the authors did not analyze fibroblasts derived from skin lesions, it is obvious that the phylloid hypermelanosis of this patient reflects cutaneous mosaicism. The cytogenetic findings documented by Oiso et al. [1] are particularly interesting because aberrations involving chromosome 13 have so far not been described in phylloid hyper melanosis, but only in its counterpart, phylloid hypo melanosis, a disorder that can today be taken as a well-established entity reflecting mosaic trisomy 13 [2– 4] . In fact, most cases of phylloid hypomelanosis are caused by mosaic trisomy 13q [2, 5, 6] . Oiso et al. [1] discuss a previous report on phylloid hypermelanosis [7] . Here, I should like to review 2 additional case reports and, at the same time, explain how the story of the phylloid pattern began. Published online: January 26, 2010