Chromosomal 10Q26 trisomy resulting from paternal T(9;10)(PTER;Q26.1)

Distal 10q trisomy is a well defined but rare syndrome, and almost always the result of an unbalanced translocation. Clinical evaluation and cytogenetic molecular analyses were performed in a 6-year-old boy with developmental delay and facial dysmorphism including marked blepharophimosis. His karyotype showed an unbalanced translocation between chromosomes 9 and 10, resulting in trisomy of the distal part of the long arm of chromosome 10q26. A balanced translocation of the segment between chromosomes 9 and 10 with breakpoints at 10q26.1 and 9pter or p24.3 was found in his father, who had normal phenotype. Unlike most cases of partial 10q trisomy which have concurrent partial monosomy of one other translocated chromosome, fluorescence in situ hybridization studies revealed this case to be a pure 10q26 trisomy. The translocated 10q segments in most cases of 10q trisomy originate from the father. Imprinting effect may exist in this chromosomal syndrome; distal 10q trisomy from paternal reciprocal translocations is more compatible with life.