Sir.—The authors Pauli et al,1 in their article on the Prader-Willi syndrome, mentioned that there is abundant evidence suggesting that a deletion in chromosome 15 is probably the cause of this syndrome complex. While the authors cited many references accurately, they neglected to mention that the remaining patients, who have been diagnosed as having the Prader-Willi syndrome, do not have this particular abnormality.
A smaller subgroup may even have robertsonian-type translocation.2-4 Indeed, in two cases further chromosomal analyses of other family members disclosed a familial pattern of balanced translocation, with no other family member having the stigmas of Prader-Willi syndrome.2,3 The translocations involved at least one of the chromosome 15 complement, but no deletions were detected by highresolution banding techniques.
It would appear that more than a simple absence of q11-q12, or any other band, is necessary to explain the occurrence of the stigmas of Prader-Willi
Wu RHK, HASEN J. Prader-Willi Syndrome. Am J Dis Child. 1984;138(8):794. doi:10.1001/archpedi.1984.02140460084028