De novo dup(7)(q21q22.2) and cytogenetics of 7q21q34 duplications

Abstract

De novo dup(7)(q21q22.2) and cytogenetics of 7q21q34 duplications: We report on a constitutional dup(7)(q21q22.2) and compile 25 similar mid-7q imbalances in order to sort out relevant cytogenetic aspects. The propositus was first karyotyped elsewhere at 2 years of age and found to have a de novo 7q+ chromosome. When reassessed at 22 years of age, he exhibited overt mental disability, marked speech delay, mild short stature, frontal bossing, and mild dysmorphisms. The patient's chromosomes were analyzed in metaphases from a lymphocyte culture by means of G-banding and FISH assays with a wcp 7 and two dual probes, namely ELN (7q11)/D7S2686 (7q22) and ELN (7q11)/D7S486, D7S522 (q31). G-bands revealed a 7q21q22.2 direct duplication that was confirmed by FISH: the 7q+ was entirely painted with the wcp and had two 7q22 signals but a single 7q31 signal. Thus, the patient's karyotype was 46,XY,dup(7)(q21q22.2).ish dup(7)(q21q22.2)(wcp7+,ELN+,D7S2686++,D7S486+)dn. Among 26 interstitial duplications confined to the segment 7q21q34, 13 were contiguous de novo duplications, one was due to a de novo ins(19;7), and 12 were inherited from carriers of inter-/intrachromosomal insertions or complex rearrangements. Mean paternal and maternal ages in de novo contiguous duplications of paternal/unknown (n=9) or maternal/unknown (n=10) descent were 33.44 and 30.9 yr whereas median ages were 29 and 30, respectively. The patient's clinical picture confirms the mild or moderate phenotypical repercussion of mid-7q duplications; among 25 patients born alive, 24 (including six teenagers or older) were still alive when reported on.