Tetrasomy 13q mosaicism associated with phylloid hypomelanosis and precocious puberty

Abstract

Various forms of pigmentary dysplasias have been known to be associated with chromosomal mosaicism. One of these disorders, known as phylloid hypomelanosis, has been found to be predominantly associated with abnormalities in chromosome 13. Most of the reported literature involves mosaic trisomy 13 with clinical evidence of abnormal pigmentation in the form of leaf-like or oblong achromic macules following Blaschko's lines. Here, we report on an 8-year-old girl with phylloid hypomelanosis and precocious puberty who was found to have mosaicism for tetrasomy 13q in the form of inverted dup(13)(q21) on her skin fibroblasts as well as peripheral blood karyotype. A higher resolution (244K) chromosomal microarray was done on DNA from skin fibroblasts confirming the breakpoint and gain of distal 13q, which made her tetrasomic for 13q21-qter. This is the first-ever reported association of tetrasomy 13q with phylloid hypomelanosis and precocious puberty. Our report further emphasizes the need to exclude any type of abnormalities of chromosome 13 in patients with phylloid hypopigmentation.

FIG. 1

Phylloid pattern of hypopigmentation. Note the leaf like as well as oval thumb print like hypopigmented macules on the front of chest and abdomen; and back. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.].

FIG. 2

a: Idiogram of chromosome 13 illustrating the inverted duplication. b: G-banding of chromosomes of cultured skin fibroblasts, showing the extra chromosome 13. This was seen in 85% of cells. The rest of the cells had a normal female karyotype.