[X chromosome with deletion of the long arm].

The authors review cases published in the literature having had a case of chromosome abnormality due to deletion of the long arm of an X. There are very few such cases. After they had indexed the somatic and chromosomal results that have been revealed, they conclude that, with the exception of dysmorphias, it is not possible to correlate the lesions that have been found with the localisation on the chromosome X. These lesions are very minor when the long arm is missing, which is contrary to the lesions that are found when the short arm has been lost. The authors draw attention to the value of modern methods of chromosome localisation. By them, marking of the break in the band 21 of the long arm as well as the diagnosis of late replication of chromosome X is made possible. A bibliography is given.