Familial Essential Thrombocythemia Associated With One-Base Deletion in the 5′-Untranslated Region of theThrombopoietin Gene

Abstract Familial essential thrombocythemia (ET) is inherited in an autosomal-dominant manner. This finding implies that familial ET may arise as a consequence of a mutation(s) that activates platelet production. In 1994, the thrombopoietin (TPO) gene was isolated and cloned. The TPO-TPO receptor, encoded for by thec-mpl gene, are essential regulators of thrombopoiesis. Alterations of TPO or c-Mpl thus may constitute a pathogenic event leading to familial ET. In a case of familial ET presented in our institute, serum TPO levels were significantly elevated in affected members of the family as compared with nonaffected members. Moreover, we identified a one-base deletion in the 5′-untranslated region of theTPO gene in affected but not in nonaffected family members. In vitro experiments showed that the identified mutation increased TPO production. Based on our findings, we propose that this region of theTPO gene may play a crucial role in regulating TPO expression. Our results strongly suggest that the identified mutation leads to familial ET. © 1998 by The American Society of Hematology.