Quiz on HbSC Disease

Which of the following is/are true?

HbSC is a type of sickle cell anemia

HbSC is a type of sickle cell disease

Both HbS and HbC are caused by a single nucleotide mutation (GAG/GTG) in the sixth codon of the β-globin gene

HbSC is a form of thalassemia

What is the evolutionary signficance of the HbC allele?

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Protection against malaria infection

True or false: Like HbSS, HbSC is a sickling syndrome, associated with potentially severe morbidities that warrant surveillance and intervention.

True

False

Why is HbAS and HbAC clinically silent wheras HbSC is not?

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Although HbAC and HbAS are asymptomatic, their combination in HbSC is symptomatic because HbC-mediated dehydration of erythrocytes leads to polymerization of HbS and red cell sickling

Regarding the CBC in patients with HbSC, which of the following is/are true?

About 70% have anemia, though Hb rarely < 10 g/dL

Macrocytosis

Usually these patients have microcytosis (unless they are taking hydroxyurea).

Leukocytosis is less pronounced or absent in HbSC compared to HbSS

Thrombocytopenia may occur

Platelet counts may be normal, but mild to moderate thrombocytopenia occurs in patients with splenomegaly and hypersplenism.

Elevated MCHC

Not seen in the cases representative CBCs shown in the tutorial, but hyperchromia may occur.

What is the most prominent finding on peripheral smear in patients with HbSC?

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Target cells

True or false: Patients with HbSC rarely develop acute pain crises.

True

False

Pain incidence less than in those with HbSS, but still significant (at least 50% of people with HbSC report a painful episode requiring a hospital visit)

What chronic complication is more common in HbSC vs. HbSS?

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Proliferative sickle retinopathy

True or false: Hydroxyurea is contraindicated in patients with HbSC.

True

False

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