OBJECTIVETo report a true hermaphroditism due to a teragametic chimerism and to discuss the pathogenesis of tetragametic chimerism.

METHODSChromosomal analysis and fluorescence in situ hybridization(FISH) were carried out on the lymphocytes from the blood and on the fibroblasts from the cultured skin and on fibroblasts from two different kinds of gonadal tissues of the patient with ambiguous genitalia respectively. Blood groups, human leukocyte antigen (HLA) haplotyping and 77 short tandem repeat (STR) microsatellite markers were tested. The two kinds of tissues in the gonad were detected by histopathological examination. Blood groups, HLA haplotying and 77 STR microsatellite markers parents of the patient's were also analyzed.

RESULTSEither 46,XX or 46,XY karyotype was found in the lymphocytes of the blood and in the fibroblasts of the cultured skin and of the two different kinds of gonadal tissues. Two X chromosome-specific signals or one X and one Y signal were detected in each interphase nucleus by FISH from the lymphocytes of the blood and the fibroblasts of three different tissue cultures. The karyotype of the 46,XY cell line predominated in all cultures except the cultured-fibroblasts from yellow gonadal tissues. STR marker analysis, ABO grouping and HLA study from the patient were identified a single haplotype in the patient from the mother and two different haplotypes from the father. Two kinds of tissues in the gonad were observed by histopathological examination. The yellow tissue was ovary and the white one was testis.

CONCLUSIONSHistopathological examination and chromosomal analysis combined with FISH are very useful methods for the diagnosis of true hermaphroditism. Blood typing, HLA and short tandem repeat microsatellite markers afford strong evidence for confirming tetragametic chimerism. The mechanism of tetragametic chimerism in true hermaphroditism can be explained by a parthenogenetic division of a haploid nucleu into two identical gametes, followed by fertilization with both X and Y spermatozoa and then developed into an organism.