T cell acute lymphoblastic leukemia arising from familial platelet disorder.

Familial platelet disorder (FPD) is a rare autosomal dominant disorder which causes moderate thrombocytopenia with or without impaired platelet function. Patients have a propensity to develop acute myeloid leukemia (AML), and various types of second hits have been postulated in the evolution to AML. However, only a few cases of acute lymphoblastic leukemia (ALL) have been reported thus far. Here, we report a family of FPD with a germ-line hemi-allelic mutation R174X in the RUNX1 gene. The proband of the family developed AML and her son had ALL of the T cell lineage. The balanced translocation t(1;7)(p34.1;q22) was detected in the lymphoblasts from the patient with ALL. This translocation was not seen in any other affected members of the family or in the bone marrow sample of this patient in complete remission. Taken together, t(1;7)(p34.1;q22) is thought to be one of the somatic second hits that predisposes FPD to acute leukemia with T cell phenotype.