engleski

Clinical, cytogenetic and molecular characterization of ring chromosome 9 formation due to inverted duplication and terminal deletion

Ring chromosome 9 is a rare chromosome aberration associated with variable phenotype that may include growth and psychomotor retardation, microcephaly, dysmorphic facial features, heart malformation, ambiguous genitalia, limb and skeletal defects. The majority of ring (9) cases arise from deletions of the chromosome with breakpoint positions between 9p22-9p24 and 9q33- q34, followed by the fusion of the ends of terminal segments. Very rarely other structural aberrations are involved. Here we describe a XY sex-reversed patient carrying ring chromosome 9 with additional material on 9p. High resolution banding suggested the presence of a duplication of band p23. Fluorescent in situ hybridization (FISH) analysis with whole chromosome painting probe for chromosome 9 excluded an insertion or a translocation from other chromosomes. The analysis with TelVision 9p and 9q probes identified the subtelomere - specific sequences on 9q but failed to detect a hybridization signal on 9p. The breakpoint positions and the size and location of duplication were further analyzed by molecular techniques using microsatellite DNA markers and multiplex ligation dependent probe amplification (MLPA). The karyotype was designated as 46, XY, r(9)(p24 ; q34.3)inv dup(9)(p24p22)mat. From 24 cases of ring (9) reported so far, there is only one case which included distal 9p duplication. This case highlights the importance of using combined molecular and cytogenetic techniques for accurate characterization of rare chromosomal rearrangements in order to make possible genotype- phenotype correlations and to understand the genetic mechanisms involved.

ring chromosome 9; duplication 9p; XY sex reversal

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