Among 16 patients with Down's syndrome (DS) and acute leukemia admitted to our department during a ten year period, 6 were diagnosed as acute megakaryoblastic leukemia (AMkL). The diagnosis was based on clinical and hematologic criteria, confirmed in three patients with the use of monoclonal antibodies (MoAb) specific for megakaryocytic antigens. In these three, and in a fourth patient, the leukemic blasts were positive for other myeloid, lymphoid and erythroid markers in MoAb testing. We suggest that AMkL in DS is a mixed lineage leukemia with blasts presenting a variety of cell surface antigens, indicating origin from an early progenitor cell with the capability of megakaryocytic differentiation. Of the 6 patients with AMkL, 4 treated with standard AML protocols are in complete continuing remission (CCR) with observation periods from 57+ to 148+ months.

In a 10-year study of T-cell acute lymphoblastic leukemias (T-ALL) in children, we have identified five cases expressing the T-cell receptor tau delta (TCR tau delta). The incidence (26%) of TCR tau delta+T-cell leukemias in our material was high. Clinically, the TCR tau delta+ leukemias represented a distinct subgroup of T-cell leukemias. Mean age at onset of disease, 1.8 years, was remarkably low for mature T-cell leukemias. White blood cell counts were high, lymph node enlargements were discrete, and no mediastinal tumors were seen. Four of five TCR tau delta+ leukemias carried rearrangements of the C tau 2 gene, and transcribed the T-early alpha genetic element.

C-reactive protein (CRP) concentrations were determined in a prospective fashion in 50 children with malignant disease. In 35 children with active and aggressive disease, but without signs of infection, no significant increase in CRP was detected. Neither did aggressive cytostatic therapy (70 courses) in non-infected children result in an increase. In bacteriologically proven, and in clinical sepsis-suspected cases, CRP values increased in all cases to levels above 100 mg/l (normal values less than 5 mg/l). Effective antibiotic therapy resulted in a prompt decline in CRP. Viral infections resulted in a much smaller increase. We conclude that serial measurements of CRP in these immunosuppressed children are of great help in monitoring infections and defining the group that needs antibiotic therapy. The measurement is also a good indicator of the effectiveness of the antibiotic therapy chosen.

In a 10-year study of T-cell acute lymphoblastic leukemias (T-ALL) in children, we have identified five cases expressing the T-cell receptor tau delta (TCR tau delta). The incidence (26%) of TCR tau delta+T-cell leukemias in our material was high. Clinically, the TCR tau delta+ leukemias represented a distinct subgroup of T-cell leukemias. Mean age at onset of disease, 1.8 years, was remarkably low for mature T-cell leukemias. White blood cell counts were high, lymph node enlargements were discrete, and no mediastinal tumors were seen. Four of five TCR tau delta+ leukemias carried rearrangements of the C tau 2 gene, and transcribed the T-early alpha genetic element.

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