Transient myeloid metaplasia associated with an unusual hemoglobin in a newborn infant.

A newborn infant presented with hepatosplenomegaly, rash, anemia, and leukocytosis at one day of age and manifested characteristic myeloid metaplasia by one mouth of life. Vitamin B12 and leukocyte alkaline phosphatase were elevated and platelet aggregation was impaired. Myelofibrosis was not present and neutrophil function was preserved. An unidentified high isoelectric point hemoglobin with unusual chromatographic and electrophoretic behaviors was found to comprise 12% of the total hemoglobin. The myeloid metaplasia and mutant hemoglobin disappeared over the subsequent months without biochemical or clinical residual. The available evidence was consistent with the mutant hemoglobin representing either a gamma chain or clonal embryonic chain variant. The inability to clarify prognostic factors in these unusual myeloproliferative syndromes suggests caution in the initiation of cytotoxic therapy.