Partial tetrasomy 9 in an infant with clinical and radiological evidence of multiple joint dislocations.

We report on an infant with partial tetrasomy of chromosome 9 due to the presence in her peripheral lymphocytes and in 55% of skin fibroblasts of an isochromosome 9 comprised of the p arm and of a portion of the q arm extending to band q21.1. The phenotype is comparable to that of other cases with a similar chromosome aberration, with multiple joint dislocations as a prominent manifestation.