PAT-4. Hemoglobin S/Montgomery trait masquerading as sickle cell trait.

We report a case of a 5-month-old infant referred for hemoglobin electrophoresis to follow-up an abnormal newborn screen. His CBC was as follows: red cell count 5.08 M/[micro]L, hemoglobin 12.3 g/dL, hematocrit 36.3%, MCV 72 fL. The patient was asymptomatic. Hemoglobin electrophoresis revealed a pattern suggestive of sickle cell trait but with an abnormal distribution. Alkaline and acid gel electrophoresis using the Beckman Paragon system was performed according to the manufacturer's procedure. Isoelectric focusing (IEF) and high performance liquid chromatography (HPLC) using the Bio-Rad Variant beta-Thal Short Program were performed by the North Carolina State Laboratory. The patterns obtained were compared to that of the mother who had been previously worked-up by Mayo Medical Laboratories. Alkaline gel electrophoresis revealed three bands migrating as hemoglobins A1 (40.8%), S (49.6%) and A2 (9.6%). Acid gel electrophoresis revealed bands migrating as hemoglobins A and S with a faint band migrating between hemoglobins S and C. HPLC revealed the following: A1 peak (45.5%) with a retention time of 2.5 minutes, A2 peak (2.9%) with a retention time of 3.6 minutes, S-window (34.6%) with a retention time of 4.5 minutes and C-window (5.1%) with a retention time of 5.0 minutes. IEF revealed a tiny hemoglobin variant between F and S and an abnormal S peak. We describe a case of co-inheritance of hemoglobin S and Montgomery traits identical to the mother's pattern. Hemoglobin Montgomery is an alpha chain variant that co-migrates on alkaline gel electrophoresis and HPLC with hemoglobin S and with hemoglobin A1 on acid gel electrophoresis. Hemoglobin S-Montgomery hybrid forms a minute band that migrates with hemoglobin A2 on alkaline gel electrophoresis and between hemoglobin S and hemoglobin C on acid gel electrophoresis. On HPLC, it migrates in the C-window. Hemoglobin Montgomery/hemoglobin S trait is clinically silent.

Chukwuma O. Onyeagocha, MD, Yvonne F. Posey, MD, and Paul G. Catrou, MD. Brody School of Medicine, East Carolina University, Greenville, NC.