Myelodysplastic syndrome with acquired hemoglobin H disease. Evolution through megakaryoblastic transformation into myelofibrosis.

A 64-year-old man was found to have a hemolytic anemia with a hematocrit of 0.28 (28%) during a routine evaluation. One month before this his hematocrit had been normal. Further studies revealed a myelodysplastic syndrome and acquired hemoglobin H disease. Eighteen months later this transformed into acute megakaryoblastic leukemia with disappearance of hemoglobin H, and shortly thereafter he had myelofibrosis develop. Acquired hemoglobin H disease, which is an alpha-thalassemia-like syndrome, results in the formation of an unstable hemoglobin composed of beta chain tetramers. This condition has been associated with preleukemia, sickle cell anemia, and hematologic malignancies. Although idiopathic myelofibrosis also has been described as a setting in which this thalassemic syndrome occurs, the present case is unusual in that the myelofibrosis was preceded by refractory anemia with leukemic transformation.