Snapshot A 25-year-old immigrant from Nigeria presents to the clinic with complaints of occasional fatigue. He has no other symptoms and denies any unexpected weight loss or night sweats. On exam, he has no lymphadenopathy. He does have mild splenomegaly and some conjunctival pallor. Labs reveal increased MCHC with intracellular crystals seen on blood smear. Introduction Hemoglobinopathy with extravascular hemolysis hemoglobin C trait (HbAC) with no clinical symptoms hemoglobin C disease with mild hemolytic anemia and splenomegaly Hb C is a structural variant of normal hemoglobin (Hb A) Genetics autosomal recessive of β-Hb chain mutation glutamic acid → lysine at position 6 recall sickle cell anemia is glutamic acid → valine at same position Pathogenesis Hb C is less soluble and crystalizes ↑ blood viscosity ↑ cellular rigidity shortened red cell survival Epidemiology common in Africa, southern Europe, South America, and Central America Potentially protects against malaria If co-inherited with Hb S (structural abnormality seen in sickle cell disease) Hb SC is less severe than Hb SS vaso-occlusive episodes vascular retinopathy avascular necrosis of femoral head Presentation HbAC asymptomatic Hb C mild hemolytic anemia splenomegaly function is unaffected cholelithiasis with pigmented gallstones more common Evaluation Diagnostic hemoglobin electrophoresis or high-performance liquid chromatography mostly Hb C absent Hb A ↑ Hb F (fetal Hb) ↑ MCHC may be noted Peripheral blood smear may show intracellular crystals may show target cells Markers of hemolysis ↑ LDH ↑ reticulocyte count ↑ indirect bilirubin Differential Diagnosis Autoimmune hemolytic anemia Sickle cell anemia Thalassemias Treatment Supportive care folic acid supplementation Prognosis, Prevention, and Complications Prognosis typically normal if co-inherited with hemoglobin S, life expectancy is in the 60s