Mosaic supernumerary inv dup(15) chromosome with four copies of the P gene in a boy with pigmentary dysplasia.

Association of the pink-eye-dilution gene (P) with hypopigmentation is seen in patients who have oculocutaneous albinism type 2 (OCA2) and Prader-Willi syndrome (PWS) or Angelman syndrome (AS). However, it remains unknown whether duplication or amplification of the P gene causes hyperpigmentation. We previously reported a woman who had hyperpigmentation with a duplication of the proximal part of 15q, including the P gene. Here, we describe an additional patient with mosaicism of inv dup(15) and clinical manifestations of severe psychmoter retardation, epilepsy, and pigmentary dysplasia showing mottled and linear patterns of hyperpigmentation. His karyotype was 47,XY,+idic(15)(pter-->q14::q14-->pter)[38]/46,XY[12] de novo. Chromosomal fluorescence in situ hybridization (FISH) showed six copies of the P gene. Therefore, his cutaneous mosaicism might be caused by the presence of both normal and hyperpigmented skin due to multicopies of the P gene.