Occurrence of sex chromosome mosaicism and translocation Down's syndrome in the same family

Abstract

The proband in this family has translocation Down's Syndrome 46, XX, t(14;21)(pll;qll), and this translocation was present in other family members. Sex chromosome mosaicism was demonstrated in three generations of the family, providing another example of familial mosaicism. There was also excessive foetal wastage in different family members. It was not possible to assign one common aetiological factor to account for these various abnormalities. Dermatoglyphic studies showed dominant inheritance of finger‐tip arch patterns in one branch of the family.

Two fertile Turner women in a family

“…Concerning the present cases, perhaps the presence of sex chromosome mosaicism in the mother predisposes to the structural rearrangement in the germ cells, and to a later postzygotic non-disjunction (Smith & Elliot 1980, Jackson et al 1975). Alternately, a random association of two different sex chromosome mosaicisms in the same family could occur.…”

Familial sex chromosome mosaicism (yes) and interchromosomal effects (no)

“…", we gave a negative answer in 1977 (Hecht & Patil). We now wish to reconsider this question in view of the paper by Smith & Elliott (1980) on the occurrence of sex chromosome mosaicism and a t(14q21q) translocation segregating in the same family, since the authors suggest that an interchromo-soma1 effect "would provide a common basis for the various abnormalities detected" in the family.…”

“…The report by Smith & Elliott (1980), together with a review of the literature, bears on several points: (1) Translocation t(14q21q): This is the commonest Dq2lq translocation causing Down syndrome (Hecht et al 1968 and1971). Smith & Elliott (1980) provide additional data indicating that the large majority of children born of parents carrying this translocation are phenotypically normal.…”

“…(2) Familial chromosome mosaicism: At least 23 families with familial chromosome mosaicism have been reported (reviewed by Hsu et al (1970) and Smith & Elliott (1980)). There is now no doubt that familial chromosome mosaicism occurs.…”

“…(4) Segregation of t(14q21q) and familial (SCM): The autosomal translocation t(14q 21q) and familial SCM are segregating independently in the family described by Smith & Elliott (1980). Independent segregation is especially evident in the collateral branch of the family in which there is SCM without the translocation.…”