Female; age, 21 years; Hb, 197 g/L; Ht, 0,59; RBC 6,35 × 1012/L; platelets, 184 × 109/L; EPO, 73.4 IU/L; smoking; several thromboembolic events; pulmonary hypertension; erythrocytosis since childhood; phlebotomy; anticoagulation therapy. The gene discussed is GSTM1; the disease is pulmonary arterial hypertension.