Partial trisomy 13: the myth of nonmongoloid trisomy G.

Reexamination of the chromosomes of a patient previously reported as having trisomy 22 yielded a partial trisomy of chromosome 13. Observations led to the conclusion that not every trisomy of a small acrocentric autosome in an individual without mongoloid features represents trisomy 22. Chromosomal analysis, preferably with a high resolution banding, of the parents may help in establishing the correct provenance of the extra chromosomal fragment. The clinical picture of partial trisomy of the proximal portion of chromosome 13 is fairly typical, yet by no means pathognomonic.