Unbalanced segregation of a complex four-break 5q23-31 insertion in the 5p13 band in a malformed child

Abstract

A rec(5)dup(5)(q23.2q31.3) inherited from a maternal ins(5)(p13.1q23.2q31.3) was detected in a 4-month-old male child who showed hypotonia, microcephaly, cardiac defects, pulmonary hypoplasia and stenosis, bilateral hydronephrosis, hydrocele, testicular hypoplasia and phimosis. Dysmorphisms were also observed. We compare the clinical characteristics of our patient with those of the previously reported dup5q cases in an attempt to define the phenotype-karyotype correlation. The maternal insertion responsible for the duplicated 5q23.2-31.3 region in the child was characterized in detail by FISH analysis, which identified a complex rearrangement involving four breakpoints (bkp's): a 5q segment excised following breakage at 5q23.2 and 5q31.3 became inverted and inserted at 5p13.1, probably coincidentally with an internal breakage at 5q23.3 causing a 180 degrees rotation of the two subsegments. The mother's karyotype was consequently defined as 46,XX, ins(5)(pter --> p13.1 Colon, two colons q23.3 --> q23.2 Colon, two colons q31.3 --> q23.3 Colon, two colons p13.1 --> q23.2 Colon, two colons q31.3 --> qter). There are clusters of Alu sequences in the genomic clones spanning all the four bkp's, suggesting their possible involvement in the rearrangement. No clinical phenotype was associated with this balanced rearrangement in the mother and a number of other carriers in the same family.