Hemoglobin K-Woolwich (Hb KW): Its Combination with Sickle Cell Trait

Hemoglobin K-Woolwich (Hb KW) is a rare hemoglobin variant with very few cases reported. It is most prevalent in West African countries, particularly Nigeria, Ghana, and the Ivory Coast. Some reports suggest Hb KW may be a clinically benign trait, whereas others indicate it may behave similarly to a β+ thalassemia. The combination of hemoglobin S and hemoglobin KW (Hb S/KW) is a rare double heterozygous disorder with little known clinical characteristics. We report the hematologic and clinical data on three patients with Hb S/KW to help describe the characteristics of this patient population. The first two cases represent first cousins, ages 3 and 2 years. They are clinically asymptomatic. They have normal hemoglobin and mean corpuscle volume (MCV) levels without reticulocytosis. The third case is of a 14-year-old male who is non-anemic with no microcytosis. He has been clinically well except for abdominal pain upon dehydration. On hemoglobin electrophoresis, these patients have Hb S levels slightly higher than typically observed with sickle cell trait and a delay of hemoglobin F to adult levels. There exists a need for more reports to better delineate the clinical course and management of these patients.