Complex sentence: Thalassemia can cause significant complications, including anaemia, iron overload, bone deformities and cardiovascular illness, thalassemia may confer a degree of protection against malaria, which is or was prevalent in the regions where the trait is common.
Split into simpler sentences: Thalassemia can cause significant complications, including anaemia, iron overload, bone deformities and cardiovascular illness. However this inherited disease of red blood cells may confer a degree of protection against malaria, which is or was prevalent in the regions where the trait is common.