The sickle cell anemia is a condition caused by a genetic mutation. The condition of sickle cell anemia leads to the change in the shape of red blood cells. In this case, the biconcave shape of the RBCs is changed to sickle shaped.
The sickle shaped RBCs cannot pass through the small blood vessels, especially microvasculature. Apart from anemia, the blocking of the microvasculature is the most common problem seen in sickle cell anemia.
Hence, the response related to obstruction of the blood vessels is correct.