What would the RBCs of someone heterozygous for sickle cell anemia look like? Would half of the RBCs look normal, and the other half sickled? Or would all of the RBCs have slight deformation/sickling? Thanks!

The peripheral smear in a patient with sickle cell trait typically appears normal (see Cecil Medicine Ch. 166). Each cell has only 30-40% HbS, and so the polymer that causes the sickling doesn't usually occur. You can find some examples online of smears with target cells and maybe one sickled cell, but these are the exceptions to the rule. This is one of the reasons a smear is not a good screening tool for sickle cell trait.

To clarify, RBCs in the blood of a patient with sickle cell disease aren't all abnormal either. See this smear from this case published on the NEJM blog:

![enter image description here](

Again, this is sickle cell **disease** , not trait, and you see many normal RBCs, even from this patient (honestly, it's not clear whether this is that patient's smear, but this would be typical). In sickle cell trait, the smear would likely be normal (image from webpath tutorial at the university of utah):

![enter image description here](