Aa Amyloidosis in a Patient with Essential Thrombocythemia and Sclerosing Angiomatoid Nodular Transformation of the Spleen

Abstract

Introduction Sclerosing angiomatoid nodular transformation (SANT) of the spleen is a rare condition with unknown pathogenesis, which is sometimes associated with hematological disorders. We present the case of renal and splenic AA amyloidosis associated with SANT and essential thrombocythemia – a previously unreported combination of pathologies. Case description A 42-year-old Caucasian woman presented with a 6-year history of progressive thrombocytosis, low-grade fever, and elevated C-reactive protein (CRP). An abdominal ultrasound discovered a splenic mass, and a bone marrow biopsy revealed megakaryocytosis with atypical features. Under interferon-α treatment, her fever resolved and her platelet count decreased, but the CRP remained elevated. Within 2.5 years she developed nephrotic syndrome and kidney failure. A kidney biopsy revealed amyloidosis. She was started on hemodialysis and underwent a splenectomy. Splenic pathology revealed SANT and AA amyloidosis of the spleen. Further review of her biopsy specimens confirmed renal AA amyloidosis and myeloproliferative disorder. Polymerase chain reaction studies showed a JAK2 V617F mutation in 1% of nucleated cells. Anti-Epstein-Barr virus (EBV) immunoglobulin G (IgG)-Epstein-Barr nuclear antigen (EBNA) and IgG-viral capsid antigen were >600 U/mL. At the latest follow-up visit 1 year after the splenectomy, she is doing well; her platelet count and CRP are normal. Conclusions Our patient has SANT and essential thrombocythemia associated with AA amyloidosis. The high titers of anti-EBV IgG suggest that chronic EBV infection may have been causative for the former 2 conditions. The return of her high CRP level to the normal range after surgical removal of the pseudotumor may suggest an association of AA amyloidosis with SANT.