Down syndrome with trisomy in one triplet.

The case presented here may be the first identified report of Down syndrome with 21 trisomy in one child of triplets. One triplet died at 1 month of age; his facial appearance was not typical of Down syndrome. Detailed testing of blood groups suggested identical origin in the remaining two children. However, the fluorescent banding technique of chromosome, one-way mixed lymphocyte culture test, and HLA typing were suggestive of dizygotic orgin. Skin transplant studies supported this contention.