[Concordant leukemia in identical twins (author's transl)].

We report female monozygous twins who developed acute lymphoblastic leukemia at the age of 5 1/2 years. The diagnosis in the first twin was made after pallor, lethargy, and petechiae developed. The diagnosis in the second twin was made two days later when a whole blood count was taken. The lymphoblasts of both patients showed with the exception of the PAS-reaction identical morphological, cytochemical, and immunological results. The PAS-reaction was positive in 55% of the lymphoblasts in one twin, negativ in the lymphoblasts of the other twin. Both patients are in continuous complete remission 14 months after diagnosis. The risk of leukemia is high in the other monozygous twin when one of the twins has already developed leukemia. In the literature it is estimated to be 1 : 5. The diagnosis after the second year of life is rarely made at the same time. There is only one previous report of this occuring in a case of acute myeloblastic leukemia in 4 1/2 year old monozygous twins.