I certainly agree with Dr. Sennholz. Individuals who have repeated transfusions are exposed to more antigens from the donor blood, so subsequent matched blood transfusions can be more complicated to prepare as additional subantigens (minor antigens) must be screened for, as these can cause transfusion reactions (fevers, shortness of breath, etc).

Additionally, individuals who have chronic transfusion therapy can develop transfusional iron overload in which the body has accumulated too much iron. The iron from the blood transfusions can accumulate in the liver, causing liver dysfunction and fibrosis. This complication can be monitored by following liver function enzymes and some imaging tests.

Reference:

http://www.irontoxicity.net/causes-of-iron-overload/transfusional-iron-overload.jsp