A dispermic chimerism in a 2-year-old Caucasian boy

Detection of two different cell populations in a child is a rare event. The following case of a dispermic chimera was diagnosed before surgery due to problems in blood group determination. A 2-year-old phenotypically male chi ld was admitted for correction of a penoscrotal hypospadia and unilateral c ryptorchism. During presurgical laboratory investigation, difficulties in b lood group determination occurred. Blood group typing was performed by the DiaMed-ID Micro Typing System and by FAGS. Additionally, cytogenetic analys is of lymphocytes and analysis of DNA polymorphisms in different tissues we re performed. Two populations of red blood cells were detected, 0 cells acc ounting for 75% and B cells for 25%. Analysis of DNA-PCR polymorphisms in l ymphocytes, nails, and in cells of the oral mucous membrane demonstrated a chimerism, with two alleles inherited from the father and one from the moth er. A cytogenetic analysis of cultured lymphocytes showed a mosaic 46,XY/46 ,XX. Surgery revealed a prostatic utricle grade III, also called pseudovagi na; genitography confirmed a vagina. Bilateral gonad biopsy showed a testis on one side and an ovary on the other. This case of chimerism represents a true hermaphroditism that most probably developed by double fertilization of one or more egg nuclei by two sperms.