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Editor—The clinical findings associated with 7p duplication have been well delineated. They comprise large fontanelles and sutures, hypertelorism, large, apparently low set ears, high arched palate, hip joint dislocation or contractures, a high frequency of cardiac septal defect, and mental retardation.1-5 It usually results from malsegregation of a parental balanced translocation or through abnormal recombination caused by a parental inversion. Some cases, however, result from a partial de novo 7p duplication.6-15 Because these cases represent pure 7p segmental imbalances, they are of great interest in phenotype-genotype correlation studies.
Here we present a case of pure 7p duplication resulting from an unbalanced inverted insertion of segment 7p13-p21.2 into the short arm of a chromosome 8. A comparative analysis of our case with those published previously suggests that the 7p21.1-p21.2 region might contain a critical region for the 7p duplication syndrome. Moreover, the presence in our patient of some opposite features of Saethre-Chotzen syndrome, which is the result of haploinsufficiency of the TWIST gene,16 17 suggests that these findings may result from a triple dosage of this particular gene.
The patient, a 24 year old man, was referred to us for further investigation because he had dysmorphic features and was mentally retarded. He was the fourth child of healthy, non-consanguineous, Lebanese parents. At birth, the mother was 26 years old and the father 31 years old. The family history was unremarkable. Pregnancy and delivery at term had been uneventful. Birth weight was 3800 g (75th centile) and length 58 cm (97th centile). A right talipes equinovarus was noted at birth. The baby was breast fed and discharged from hospital on the third day of life. A severe delay in developmental milestones was observed as he walked at 5 years of age and said only a few words …