it s very important to differentiate this anemia from any type of hemolytic anemia , which means the red blood cells being destroyed , in simple words the causes of profound anemia to this child are few : either a profound destruction : which causes increase biliruben along with reticulocyte count ( immature red blood cells , positive direct coombs test ) or the most likely here is the inability of the bone marrow to produce red blood cells either due to infection ( such as Parvovirus b19) which causes a disease called ( red cell Aplasia ) in which the number of RBCS are very few . OR what is cakked transient erythroblastopenia of childhood , which causes the red cells to markedly decrease in number ( pure red cell Aplasia) bone marrow biopsy is some times needed to exclude other causes , but usually the transient erythroblastopenia of childhood requires one blood transfusion or 2 at max and then the child improves , keeping in mind it s the most common cause of pure red cell Aplasia in children I hope this helps