Chronic myelogenous leukemia occurring in two brothers diagnosed 26 years apart

Chronic myelogenous leukemia (CML) is characterized by the presence of the chromosomal abnormality t(9;22)(q34;q11), which is detected in more than 90% of cases. Despite great strides in our understanding of this disease, few predisposing etiologic factors have been identified. We report on the case of a 45-year-old man with Philadelphia chromosome–positive, BCR-ABL fusion–positive chronic-phase CML, whose brother had succumbed to the same disease 22 years earlier. While a coincidental familial occurrence cannot be excluded in this case, we believe that this report underscores the need for further investigation of possible unknown environmental or heritable etiologic factors in this disease.