Inherited X-chromosome inverted tandem duplication in a male traced to a grandparental mitotic error

S. Schwartz, M. F. Schwartz, S. R. Panny, C. J. Peterson, E. Waters, M. M. Cohen

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


A male infant was referred for cytogenetic evaluation because of dysmorphic features and developmental delay. In both lymphocytes and skin fibroblasts, a modal number of 46 chromosomes was obtained with an obvious elongation of the long arm of the X chromosome (Xq+). Studies of seven members in 3 generations of this family showed that the proband's mother, sister, and maternal grandmother were phenotypically normal carriers of this abnormal X chromosome. High resolution GTG- and RBG-banding defined the extra chromatin material as an inverted duplication of Xq21→Xq24. This was supported by an approximate twofold increase in α-galactosidase A activity, localized to Xq21-q24, observed in the proband's lymphocytes and fibroblasts. BrdU-incorporation studies of the mother's lymphocytes showed the abnormal X to be late replicating in all 100 cells studied and normal α-galactosidase A levels. Cytogenetic analysis of the maternal grandmother revealed cytogenetic mosaicism with one cell line containing the abnormal X (37%), and the other, a normal female karyotype (63%). This family is instructive since: (1) it represents only the second case of a dysmorphic male demonstrating a confirmed interstitial partial Xq duplication, and (2) the origin of this familial structural rearrangement has been traced to a grandparental mitotic error.

Original languageEnglish (US)
Pages (from-to)741-750
Number of pages10
JournalAmerican journal of human genetics
Issue number5
StatePublished - 1986
Externally publishedYes

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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