Which inheritance leads to HbSC disease?

• A. Inherit a gene for haemoglobin S and a gene for normal HbA
• B. Inherit two genes for haemoglobin S
• C. Inherit a gene for haemoglobin S and a gene for haemoglobin C
• D. Inherit a gene for HbC and HbA

Answer: (C)

HbSC disease happens when a person inherits one copy of the sickle cell allele (S) and one copy of the hemoglobin C allele (C). This makes them compound heterozygous for the beta-globin mutations, so their red blood cells contain both HbS and HbC. The combination causes sickling and related symptoms, though often milder than in sickle cell anemia.

Why the other scenarios don’t cause HbSC disease: inheriting S with a normal hemoglobin gene (A) gives sickle cell trait, usually without symptoms; inheriting two S alleles (SS) produces sickle cell anemia; inheriting C with a normal gene (A) yields HbAC trait, also typically mild or asymptomatic. Only the mix of S and C leads to HbSC disease.