Promyelocytic Leukemia in Mexican Mestizos

To the Editor:

The report by Douer et al,1 followed by the letters by Otero et al,2 Tomás and Fernández-Rañada,3 and Douer et al,4 that describe a high prevalence of M3-AML among Latinos from Spain, Mexico, Peru, Nicaragua, Venezuela, Brazil, and Italy, adds interesting data to the concept of geographic hematology,5 an area that seemed to be in extinction despite its possible significance in the etiology of certain malignancies. The term Latino describes strictly a variety of populations speaking languages derived from Latin, the language of the old Romans, mainly Italian, Spanish, and Portuguese. Because it is unlikely that there is an association of the prevalence of M3-AML with the native language of the patients, population studies should be performed to identify possible genetic markers of increased susceptibility to the disease or some other variables instead of associating it with a language. We have been interested in geographic hematology6-12 and described that in Mexico, in the Mestizo population (56% of whom have been shown to have Indian genes, 40% white genes, and 4% black genes13 ), the salient features of the geographic distribution of leukemias, as compared with white populations, are: A high prevalence of M3 and M7 leukemias,6-8 a low prevalence of pre-B acute lymphoblastic leukemia,6,9,10 a very low prevalence of chronic lymphocytic leukemia,6,11,12 and a low prevalence of hairy cell leukemia.6,11,12 Despite the fact that the genetic composition of the Mexican Mestizo population is very different from that of the inhabitants of Spain, certain similarities in the prevalence of some leukemias have been found, such as the high prevalence of M7-AML,6,7 and now the high prevalence of M3-AML.3,6,14 

In our single-institution experience with 198 patients with acute leukemia treated during a 10-year period, promyelocytic leukemia represents 20% (12/60) of all patients with myeloid leukemia, and 30% of myeloid leukemias in adolescents (age, 11 to 21 years).14 Interestingly, the current therapeutic approach using all-trans-retinoic acid as front-line therapy in M3 leukemias15 has substantially improved the prognosis of adolescents with acute myeloid leukemia14,16,17 to the point that, possibly because of the high frequency of M3-AML, adolescents with myelogenous leukemia have a better prognosis than those with lymphoblastic leukemia.14,18 These data add information about the increased prevalence of AML among Mexican Mestizos, but not Latinos.