Mom's Ulcer Bug May Up Leukemia Risk in Offspring

NEW YORK (Reuters Health) - A study for the first time hints that maternal infection with Helicobacter pylori -- the bacterium that causes most cases of stomach ulcers -- is associated with an increased risk of childhood leukemia in the offspring.

Leukemia makes up 25 percent of all childhood cancers worldwide and so-called acute lymphoblastic leukemia (ALL), the most common form of the blood cancer, comprises about 80 percent of all childhood leukemias.

The fact that ALL tends to cluster in families and with "population mixing" suggests ties between infection and childhood leukemia, Dr. Matti Lehtinen from National Public Health Institute in Oulu, Finland and colleagues explain the American Journal of Epidemiology this month.

Lehtinen and colleagues used a cohort of 550,000 mothers and their offspring to study the role of H. pylori as well as two other common bacterial pathogens -- Mycoplasma pneumoniae and Chlamydia pneumoniae -- in childhood leukemia. The subjects resided in Finland or Iceland.

Taken in isolation, neither M. pneumoniae nor Chlamydia was associated with an increased risk of childhood leukemia, the report indicates.

In contrast, the authors report, in the group from Iceland, having a mother test positive for H. pylori was associated with a 2.8-fold increased risk of childhood leukemia in the offspring. The risk was even higher (3.7-fold) when the analysis was restricted to Icelandic cases diagnosed before the age of 6 years, the results indicate.

In the group from Finland, however, H. pylori positivity was not associated with an increased childhood leukemia risk, the researchers note.

"To our knowledge," the authors conclude, "we have documented for the first time the possibility of an association between maternal H. pylori infection and risk of childhood leukemia in the offspring. Independent confirmatory studies are needed."

SOURCE: American Journal of Epidemiology October 1, 2005.