My Little Grandson Is 2 Months Old. At 1 Month,

My little grandson is 2 months old. At 1 month, he had a red blood cell count of 4.5. He was hospitalized and given transfusions. Last week, at his 2 month checkup, he was low again at 7.5. They checked him today and sent him to the hospital for transfusions again. His parents are waiting for the lab results. What could be causing this in a an otherwise healthy looking baby?