We report the case of an old Tunisian patient hospitalized for a complicated hydatic cyst of the right lung. Primary laboratory investigation showed a microcytic hypochromic anemia with an abnormal hemoglobin pattern. Hemoglobin analysis and DNA sequencing of the ␤-globin gene revealed a compound heterozygote, HbO-Arab/cd 39 ␤ •-thalassemia. This hemoglobinopathy was never diagnosed earlier. It spent undiagnosed until the patient presented with hydatic cyst. Coexistence of the two pathologies complicated the general state of the patient and led to a severe anemia. The patient has undergone a surgical therapy for the hydatic cyst and was advised to start a follow up for her hemoglobinopathy.