Another Example of Haemopoietic (Twin) Chimaerism in a Subject Unaware of Being a Twin

Abstract

SUMMARY A fourth human blood group chimaera studied in Birmingham is an example of haemopoietic (twin) chimaerism in which the subject was unaware of being a twin. Chimarerism was discovered during routine antenatal serological investigation in which it was shown that the proposita has two red cell populations, one of the rhesus genotype rr, and the other R1r. Further studies showed that she has two populations of lymphocytes, one with the female karyotye, 46XX, and the other with the male karyotype, 46XY. Skin fibroblasts were all 46XX.

Blood Group Chimeras

“…Bird et al [9] recorded a suggestion that, because the yolk sac is one ofthe earliest sites of haemopoiesis, fusion of the primitive cir culations of two yolk sacs could lead to for mation of a twin chimera with no apparent twin. However, Lassila et al [42] using chick-chick embryos distinguished by differ ent B locus antigens showed that, although yolk sac stem cells are responsible for prim itive erythrocytes, embryonic stem cells are the only progenitors of lymphocytes and permanent red cells.…”

“…P.M. [62,No.20 in table 92], and a new one, Mrs. C. C. [9], with no known twin are not included in this sec tion, but will be discussed below in the sec…”

“…Their fertility has been used to suggest that these are really twin chimeras [2,9] with a resorbed twin. However, since 2 dispermie chimeras with fibroblast karyo types alien to their phenotypic sex have proved themselves fertile, chimeras with no family members with the same A, gene is lower than would be expected from a twin chimera genetically A,, but more than would be expected from an O twin with 16% A, cells.…”

Blood Group Chimeras: A Review

“…20 in table 921, and a new one, Mrs. C.C. [9], with no known twin are not included in this section, but will be discussed below in the sec-tion on chimeras of unknown type (see Appendix 3). Ascertainment 27 ofthe 32 propositi were found through two populations of red cells.…”

Mosaicism due to myeloid lineage–restricted loss of heterozygosity as cause of spontaneous Rh phenotype splitting

“…Known reasons for such findings include hematopoietic or whole-body chimerism (presence of cells from 2 or more zygotes), mosaicism (presence of cells of different phenotypes derived from one zygote), and somatic RHD mutation. [4][5][6][7] Recently, also mosaicism involving a cell line with uniparental isodisomy for chromosome 1 was described as a reason for ambiguous RhD typing. 8 Many individuals with spontaneous Rh phenotype splitting or progressive Rh antigen loss were found to suffer from hematologic disease, such as acute or chronic myelogenous leukemia, myeloproliferative disease, or myelodysplastic syndrome, in the majority of cases without detectable cytogenetic abnormalities of chromosome 1.…”