[Bloom syndrome, constitutional and induced genetic instability in 2 cases from Argentina]. / Síndrome de Bloom, inestabilidad genética constitucional e inducida en dos casos de la Argentina.

Bloom's syndrome (BS) is a rare autosomal recessive hereditary disorder associated with pre- and postnatal growth deficiency, a characteristic facial configuration, an increased risk of chromosome instability, and an increased risk of neoplasia. BS is often lumped together with Fanconi's anaemia, ataxia telangiectasia and xeroderma pigmentosum, known as "chromosome instability syndromes". Since 1954, when Bloom's syndrome was defined, more then 100 cases have been diagnosed. The "Bloom's Syndrome International Registry" does not include any case detected in Argentina. Here, we report the cytogenetic study of a family affected by BS. Two siblings were studied. A 10-year-old boy named DaYu and a 17-year-old sister named CeYu. Both showed growth retardation from one month of age onwards, facial configuration characteristic, erythematous and sun-sensitive lesions of the skin of the face. To confirm the BS diagnosis of both, obtained from their clinical aspects, they were referred to our cytogenetic laboratory. Standard cultures of peripheral blood from DaYu and CeYu (homozygotes bl/bl) and their parents (heterozygotes bl/+) were performed for sister chromatid exchange (SCE) study. A group of 3 healthy donors (homozygotes +/+) was added for spontaneous and induced chromosomal aberration (CA) analysis. For the SCE study, bromodeoxyuridine was present in the cultures and slides were stained using the fluorescence plus Giemsa technique. For the analysis of induced CA, diepoxybutane (DEB) 0.1 microgram/mL was added 48 hours before harvesting. Both patients had a spontaneously increased rate of sister-chromatid exchanges (71.3 +/- 28.2 for DaYu and 76.9 +/- 37.9 for CeYu) similar to that found in Bloom's syndrome homozygotes.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased expression of 5q31 fragile site in a Bloom syndrome family.

In this work, we report spontaneous chromosomal breakpoints and fragile site expression induced by 5-fluorodeoxyuridine (FdUrd) and FdUrd plus caffeine in a family with Bloom's syndrome (BS) and 2 healthy donors. Standard and G-banded metaphases from each individual and each treatment were analyzed. Among the 59 common fragile sites (c-fra) identified in this work, only the frequency of 5q31 was significantly increased in the BS family with respect to healthy donors (P less than 0.005). A remarkable coincidence between the breakpoints involved in spontaneous chromosome aberrations and induced c-fra was found in BS homozygote patients. The importance of the interaction between fragile sites and chromosome rearrangements in cancer is discussed.