ETV6-related
thrombocytopenia is an autosomal dominant
thrombocytopenia that has been recently identified in a few families and has been suspected to predispose to
hematologic malignancies. To gain further information on this disorder, we searched for ETV6 mutations in the 130 families with inherited
thrombocytopenia of unknown origin from our cohort of 274 consecutive pedigrees with familial
thrombocytopenia. We identified 20 patients with ETV6-related
thrombocytopenia from seven pedigrees. They have five different ETV6 variants, including three novel mutations affecting the highly conserved E26 transformation-specific domain. The relative frequency of ETV6-related
thrombocytopenia was 2.6% in the whole case series and 4.6% among the families with known forms of inherited
thrombocytopenia. The degree of
thrombocytopenia and
bleeding tendency of the patients with ETV6-related
thrombocytopenia were mild, but four subjects developed B-cell
acute lymphoblastic leukemia during childhood, resulting in a significantly higher incidence of this condition compared to that in the general population. Clinical and laboratory findings did not identify any particular defects that could lead to the suspicion of this disorder from the routine diagnostic workup. However, at variance with most inherited
thrombocytopenias, platelets were not enlarged. In vitro studies revealed that the maturation of the patients' megakaryocytes was defective and that the patients have impaired proplatelet formation. Moreover, platelets from patients with ETV6-related
thrombocytopenia have reduced ability to spread on
fibrinogen. Since the dominant
thrombocytopenias due to mutations in RUNX1 and ANKRD26 are also characterized by normal platelet size and predispose to
hematologic malignancies, we suggest that screening for ETV6, RUNX1 and ANKRD26 mutations should be performed in all subjects with autosomal dominant
thrombocytopenia and normal platelet size.