The vanishing DZ twin and the chimera

This man was found to be a chimera of himself and his vanished twin sister, 40 years after his birth.

We report the case of a 40-year-old man diagnosed with a scleroderma-like disease. Clinical similarities with graft versus host disease prompted initial testing for chimerism employing fluorescence in situ hybridization (FISH). Female cells were observed within peripheral blood mononuclear cells from the patient.

Because maternal cells have been detected in healthy immunologically competent adults and patients with autoimmune conditions, we hypothesized that these cells were of maternal origin. Contrary to our expectations, HLA-specific quantitative PCR (QPCR) ruled out maternal microchimerism. However, HLA-specific QPCR testing was positive for the paternal HLA haplotype that the patient did not inherit. We reasoned that the most likely origin of chimerism with non-inherited paternal HLA alleles was from an unrecognized “vanished” twin. The patient had never received a blood transfusion.

This report suggests that cells from a vanished twin are a possible source of chimerism. The frequency of chimerism from this source is not yet known and whether the scleroderma-like disease observed in the patient is anecdotal or implies a potential association with autoimmune disease remains to be elucidated.

 Read whole article here

And here is a nice movie for you, featuring many people speaking about chimeras, including Dr House!  Lots of nice images of twin zygotes etc....

(Not allowed to embed, so click here)