Polycythemia vera in a child with acute lymphocytic leukemia.

A 10-year-old boy, who had been in an uninterrupted remission of acute lymphocytic leukemia (ALL) for six years, developed polycythemia vera (PV). One and a half months after detection of PV, he was found to have active leukemia. Both the polycythemia and leukemia receded with anti-leukemia therapy. Three possible explanations for the development of PV in a child with ALL are discussed: 1) PV was a part of his original ALL and recurred whtn patient relapsed. The PV phase was detected only during relapse because the patient was under close observation. 2) PV was a second neoplasm independent of ALL. 3) PV was part of a second leukemia which was different from the original leukemia; this new ALL was derived from a pluripotential cell line involving both erythroid and lymphoid elements. A precedent for this explanation has been observed in chronic myelogenous leukemia.