Eduardo S. Cantú

Unusual cytogenetic mosaicism involving chromosome 14 abnormalities in a child with an MR/MCA syndrome and abnormal pigmentation

An 8‐year‐old female child with mental retardation (MR), multiple congenital anomalies (MCA) and irregular pigmentation was shown to have karyotypic mosaicism involving chromosome 14 abnormalities. Four cell lines were found in both peripheral blood lymphocytes and skin fibroblasts and were represented by: a normal karyotype, an isopseudodicentric 14q [iso psu dic(14)], a ring 14 [r(14)], and a monosomy 14 [mono(14)]. Our results are compared with reported cases involving multiple abnormalities of specific chromosomes. Karyotypic mosaicism of comparable chromosome 14 abnormalities is rare, with only one known previous case. Detailed analysis of karyotypic mosaicism of rare chromosomal abnormalities is essential to determine meaningful correlations with specific patterns of malformation.

PIGMENTARY ABNORMALITIES AND CHROMOSOMAL AND GENETIC MOSAICISM AND CHIMERISM

We have studied nine patients who presented with pigmentary anomalies of the skin in association with other congenital malformations; in eight, we demonstrated chromosomal mosaicism in lymphocytes and/or skin fibroblasts. A review of the literature revealed 25 similar examples of an association between pigmentary anomalies and chromosomal mosaicism or chimerism. The pigmentation varied but usually followed a pattern known as Blaschko lines. Our findings indicate a relationship between aberrant skin pigmentation and chromosomal mosaicism, and suggest a developmental explanation for the pigmentary patterns seen in chromosomal or genetic mosaicism and in chimerism. Further, they emphasize the need for extensive cytogenetic investigation of patients who present with pigmentary abnormalities and associated malformations.