Haemopoeitic progenitor cell transplantation
Haemopoetic progenitor cell transplantation is used in an attempt to cure various haematological and immunological conditions. Treatment begins with ablation of the existing diseased marrow using cytotoxic drugs and/or total body irradiation. This induces pancytope nia and severe immunodeficiency risking bacterial infection, bleeding and anaemia. Total body irradiation has a number of potential late complications including thyroid underactivity, gonad underactivity, cataract formation, diarrhoea, sun burn and nausea.
During this pancytopaenic period support includes the following:
· Blood transfusion, if haemoglobin falls below 10.0 g/dL, (CMV negative if patient and donor have not had CMV). Blood is irradiated to prevent graft versus host disease.
· Platelet transfusions may be used.
· Patients are maintained in a filtered air environment. Prophylactic antibiotics and antivirals can be used. The pancytopaenia is reversed by haemopoetic progenitor cell transplantation (infusion into a peripheral vein of haemopoetic progenitors, which finds its own way to the marrow cavity and regenerates it). Grafts may be allografts (HLA matched sibling or unrelated donors) or autologous (from self) either bone marrow or more recently peripheral blood stem cell transplants and cord blood.
Allografts risk the negative effect of graft versus host disease (GVHD) where mature T cells in the transplant recognise the rest of the body as ‘nonself ’ and therefore attempt to reject it. Coupled to this is a positive phenomenon known as the graft versus leukaemia effect (GVL) where the donor marrow recognises any remaining leukaemic cells and mounts an immunological attack. Acute GVHD may occur within the first 3 months and subsequently chronic GVHD may develop. Acute GVHD affects HLA-rich tissue with desquamation of the skin, impairment of liver function and diarrhoea. Lymphocyte-depleted marrow reduces the risk of GVHD, but also eliminates the graft versus leukaemia effect and may thus increases the risk of relapse.
Chronic GVHD, which occurs after 3 months may be an extension of acute GVHD or may occur in patients who never showed clinical evidence of acute GVHD.
· Ocular manifestations: Irritation, photophobia, and SICCA syndrome.
· Gastrointestinal system: Abdominal pain dysphagia, odynophagia, weight loss, malabsorption and liver disease.
· Respiratory system: Obstructive lung disease usually nonresponsive to bronchodilator therapy.
· Neuromuscular system: Weakness, neuropathic pain, muscle cramps.
Autografts (frozen haemopoetic progenitors from the patient) is not associated with GVHD or GVL and may involve reinfusion of leukaemic cells. However, they have the advantage of availability. Peripheral stem cell transplants are now used more frequently than autologous bone marrow transplantation. They have the advantage that more progenitor cells are collected and thus rescue from pancytopenia occurs more rapidly.