Erythropoietin deficiency and relative resistance cause anaemia in post-renal transplant recipients with normal renal function.
BACKGROUND: Following successful renal transplantation, blood erythropoietin (Epo) levels peak in two phases during the first 2-3 months, and blood haemoglobin/haematocrit (HB/Hct) levels are restored to normal in a period of 2-6 months. However, some transplant recipients continue to remain anaemic in spite of normal graft function and in the absence of recognizable causes. The role of endogenous Epo production in the causation of anaemia in such patients is poorly understood and has been investigated in this study. METHODS: Twenty-three post-renal transplant recipients with stable normal renal function were studied. Eleven of these patients had normal HB/Hct levels (group 1) and served as control for the rest 12 patients with anaemia (group 2). Patients included in group 2 had no readily recognizable cause for their anaemia. Other laboratory and clinical findings were similar in both groups. Patients with erythrocytosis were excluded. Serum Epo levels were measured in all patients. Five patients in group 2 were treated with recombinant human erythropoietin (rHuEpo) and their erythropoietic response was assessed. rHuEpo was discontinued when the target Hb/Hct levels (lowest normal range) were achieved and the patients were followed up for a further period of 9-12 months. RESULTS: Five patients in group 1 had normal expected serum Epo levels whereas the other six patients had inappropriately high serum Epo levels with respect to their Hb/Hct status suggestive of relative ¿EPO resistance'. Serum Epo levels in all patients except two in group 2 were low indicative of 'Epo deficiency'. The two exceptional patients in group 2 had higher serum Epo levels in the presence of anaemia suggestive of relative ¿Epo resistance'. All five patients treated with rHUEpo responded adequately by achieving normal Hb/Hct levels. Three of them were originally ¿Epo deficient' and they reached target Hb/Hct levels in a mean period of 4 weeks, requiring a mean cumulative rHuEpo dose of 428.3 units/kg. The other two patients with higher initial serum Epo levels, and considered to be ¿Epo resistant' required an average of 11 weeks of treatment and a mean cumulative rHuEpo dose of 1582.5 units/kg, indicating an increased Epo demand. On cessation of therapy the Hb/Hct levels fell in all five patients to pretreatment values in 6 months. CONCLUSIONS: There are important variations in the endogenous Epo production in renal transplant patients with normal renal function, the cause of which is not clear. Epo deficiency and relative Epo resistance play a causative role for anaemia in some post-renal transplant recipients with stable normal renal function. They respond adequately to rHuEpo administration.