Hemoglobin SC disease
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Hemoglobin SC (HbSC) disease is a hemoglobinopathy, and a common variant of sickle cell disease (SCD). There is coinheritance of one HbS gene and one HbC gene, resulting in a milder phenotype than full-blown sickle cell disease. It most commonly manifests with a proliferative retinopathy. Painful crises, functional asplenia and osteonecrosis are also frequent sequelae.
Hemoglobin SC disease makes up almost 30% of cases of sickle cell disease in the United Kingdom and the United States 1. In some regions of West Africa, where the HbC variant arose, HbSC may form more than half of all cases of sickle cell disease 1. Globally more than 50,000 babies with HbSC are born each year.
In general, hemoglobin SC disease is viewed as a milder variant of sickle cell disease, nevertheless significant morbidity still often results.
- ocular: proliferative retinopathy commonest complication of HbSC, ~70%
- painful crises are common, seen in half of patients
- splenic: functional asplenia in 45% by the age of 12 years 1
- bone: osteonecrosis affects almost one quarter of HbSC patients
- CNS: strokes
- priapism: 20% of male patients develop this sequela
- acute and chronic lung disease
- thromboembolism: PE and DVT are more common
- gallbladder disease in 20% (cf. sickle cell disease 50%)
Inheritance of the hemoglobin S (HbS) and hemoglobin C (HbC) beta globin gene (HBB) mutations together (i.e. coinheritance) results in hemoglobin SC (HbSC) disease.