Low Erythropoietin Production in Familial Amyloidosis TTR V30M Is Not Related with Renal Congophilic Amyloid Deposition

Background: Anemia with low serum erythropoietin (EPO) is common in Portuguese transthyretin V30M amyloid polyneuropathy (FAP). Low EPO production can be observed before clinical disease. Renal amyloidosis is observed in FAP, mainly in the medulla. Renal manifestations correlate with glomerular and vascular involvement, but not with tubulointerstitial deposition. To evaluate the potential role of renal amyloid deposits in the genesis of the EPO defect in FAP, we analyzed the renal biopsies of 12 patients (5 males, 7 females, aged from 29 to 54 years) with a clinical evolution varying from 3 to 12 (mean 5.4 ± 2.8) years. Methods: Formalin-fixed, paraffin-embedded sections of renal biopsies were stained by Congo red. Amyloid deposits were assessed by a semiquantitative method based on the percentage of amyloid deposition in each renal structure. Hemoglobin, creatinine, urea, EPO and proteinuria were concomitantly evaluated and correlated with the pathological findings. Results: Renal amyloid deposits were observed in all biopsies analyzed, independently of the neuropathy score. Low serum EPO levels were not related with either the amount of amyloid deposition or the renal clinical manifestations. Conclusion: Impairment of EPO production in FAP is not directly related to renal amyloid deposits and more studies are needed to clarify this question.