A 2-year-old girl had a de novo duplication in the long arm of one chromosome 7 and an increased level of the enzyme β-glucuronidase in cultured fibroblasts. The phenotype of the girl partly overlaps those of two presumptive syndromes due to secondary partial trisomies 7q. The ratio of the enzyme activity was 1.43 to the controls, and 1.37 to her parent's values. We could not define the abnormality but suggest two alternatives: either the patient is trisomic for region q112 to q22 or for the region q22 to q34. If the second alternative is correct the locus for β-glucuronidase is possibly assigned to band 7q22.
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