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.

We report on a baby girl with absence of the left hemidiaphragm, lumbosacral myelomeningocele, syndactyly with limb deficiencies, and bilateral hydronephrosis. A similar array of malformations was described previously by Czeizel and Losonci [Hum Genet 77:203-204, 1987] in a single family which showed a transmission pattern suggesting autosomal dominant inheritance with variable expressivity. The presence of limb abnormalities and the location of the neural tube defects in these cases suggest that the underlying pathogenesis probably does not involve the same disturbances of midline field development which have been postulated to occur in the schisis association.