BMC Nephrology BioMed Central

Background The incidence and risk factors for hospitalized atrial fibrillation have not been previously assessed in a national population of dialysis patients. Methods We analyzed the United States Renal Data System (USRDS) Dialysis Morbidity and Mortality Study (DMMS) Wave II in a historical cohort study of hospitalized atrial fibrillation. Data from 3374 patients who started dialysis in 1996 with valid follow-up times were available for analysis, censored at the time of renal transplantation and followed until November 2000. Cox Regression analysis was used to model factors associated with time to first hospitalization for atrial fibrillation (ICD9 code 427.31x) adjusted for comorbidities, demographic factors, baseline laboratory values, blood pressures, dialysis modality, and cardioprotective medications. Results The incidence density of atrial fibrillation was 12.5/1000 person years. Factors associated with atrial fibrillation were older age (> = 71 years vs. <48 years), extremes (both high and low) of pre-dialysis systolic blood pressure, dialysis modality (hemodialysis vs. peritoneal dialysis), and digoxin use. Baseline use of coumadin was associated with reduced mortality in patients later hospitalized for atrial fibrillation. Conclusions Dialysis patients had a high incidence of atrial fibrillation. This risk was largely segregated among those with established risk factors for atrial fibrillation, and hemodialysis patients. Use of coumadin was associated with improved survival among patients later hospitalized for atrial fibrillation.


Background
Extra-hepatic manifestations of hepatitis C virus (HCV) infection are diverse and appear during late middle age [1][2][3]. Among these, glomerulonephritis, arthritis, dermal vasculitis and sialadenitis are thought to develop as a result of the deposition of immune complexes (IC). It is generally accepted that B-cells infected with HCV clonally expand and produce autoantibodies [4,5]. When antigenbound, these autoantibodies, along with anti-HCV antibodies that target viral epitopes on the surface of cells are known to circulate as IC. These IC may participate in the pathogenesis of HCV-associated glomerulonephritis, though it has been difficult to detect these IC clinically. While immunosuppressive agents have been used successfully to diminish the production of autoantibodies, such a strategy is contraindicated in HCV patients since it would lead to an increase in viral replication.   We herein report the case of a patient with extra-hepatic manifestations of chronic HCV infection that developed autoimmune hemolytic anemia (AIHA) prior to evident nephropathy.

Case presentation
A 66 year old man, with no prior history of blood transfusion, drug addiction, or the acquisition of tattoos, was diagnosed with hemolytic anemia in June of 2000. From the time he was 50, his yearly health check-ups have revealed faint hematuria (±) by urine dipstick testing, and he first exhibited proteinuria when he was 60 years old (see Table 1 for the patient's clinical history). At no time did the patient shows signs of liver dysfunction. Two of the patient's five brothers suffered from chronic liver disease (no further information was available) but none had a history of anemia.
In March of 2000, the patient was diagnosed with sudden onset anemia characterized by an increase in both mean corpuscular volume and corpuscular hemoglobin. Result of the Coomb's, acidified serum, sucrose hemolysis, and cold agglutinin tests were negative. Because spherocytes predominated in his hemogram and the results of his erythroresistant test (Ribiere's test) were positive, he was provisionally diagnosed as having hemolytic anemia caused by spherocytosis. Since he was asymptomatic, he was followed without medication.
Starting in September of 2000, the patient's hematuria and proteinuria progressed and his hemolysis worsened. Laboratory data began to indicate an increase in urinary protein excretion and a lowered serum protein concentration. The patient began to experience mild pretibial edema in March of 2001, at which time he was admitted to our hospital and a renal biopsy performed. Hematological tests at that time revealed the hyperchromic anemia with a macrocytic pattern and an increased numbers of reticulocytes. A hemogram (Figure 1)  Moderate levels of protein were found in the urine but serum total protein levels were slightly below the normal range. Urine dipstick testing gave a false positive result for occult blood detection. The slide precipitation test for syphilis also resulted in a false positive reading, though anti-cardiolipin β 2 GPI antibodies were absent. Hypocomplementemia with cold activation was demonstrated with the serum titer of CH50 being low though plasma titers were recoverable (his blood was collected in EDTA-containing tubes). Cryoprecipitation under cold storage (4°C, 72 hrs) followed by immunoelectrophoresis revealed the presence of a mixed type II cryogobulinemia. HCV viremia was confirmed using an HCV-RNA PCR test (genotype: 1B). Antibodies directed against HBV, HIV, EBV, and CMV were not found. An abdominal echogram revealed the absence of a splenomegaly and showed that his liver was of normal size and that it had a smooth surface. Because the patient was symptom free, he was discharged after his renal biopsy and was followed without treatment. One year later, the patient had the same degree of hemolysis (hemoglobin = 7.4 g/dl, LDH = 756 U/l, total bilirubin = 2.7 g/dl) though his creatinine clearance had decreased (69.5 ml/min.). However, his urinary protein was stable (1.6 g/day) and his serum total protein recovered into the normal range (7.1 g/dl). His liver function was near normal (AST = 57 U/l, ALT = 19 U/l, albumin = 3.5 g/dl). And his level of HCV-RNA was slightly reduced (130 KIU/ml).

Hemogram (May of 2001)
Renal histology (Figure 2 and 3): Five glomeruli were visualized in the patient's biopsy specimen. One of these glomeruli was intact while the other four, which were mildly lobulated, appeared to show a slight increase in mesangial cells and matrix. The glomerular basement membrane (GBM) was partially thickened and PAS staining revealed small spikes and bubble formation. No glomeruli had GBM cryoglobulinemic deposits. Small fibro-cellular crescents were found in two glomeruli. The proximal tubular epithelial cells contained numerous hemosiderin granules.
Immunofluorescence histochemistry demonstrated the presence of IgG in the GBM that was distributed in a course granular pattern, as well as the presence of IgA in the GBM and mesangial area. Staining for IgM and C3c was faint in the mesangial area, while C3d, C4d, C1q and fibrinogen were undetectable. Electron microscopy revealed small subepithelial deposits and a few paramesangial deposits in the glomerulus.
Renal tissue (Light microscopy, PAS stain, × 200) Figure 2 Renal tissue (Light microscopy, PAS stain, × 200). The patient's glomeruli showed partial thickening of the GBM and exhibited some mesangial proliferation. Hemosiderin deposits were seen in the cytosol of proximal tubular epithelial cells (arrowhead).

Conclusions
In our patient, IgG autoantibody, which binds to RBCs, was detected in our patient using the direct antiglobulin test (Coomb's test), leading us to conclude that AIHA was the primary pathogenic mechanism that resulted in his hemolysis. Since his serum reacted with the full panel of RBCs tested, his autoantibodies probably recognized a common RBC surface antigen. Recent studies which suggest that the possible target antigens in AIHA are band 3 or 4.1 peptides, Rh, or glycophorin A, all of which are expressed on RBCs [6][7][8]. Our patient had not been treated with any antiviral drugs, such as ribavirin ® , which have been shown to induce hemolytic anemia by a mechanism involving the oxidation-induced aggregation of band 3, leading to the binding of autologous anti-band 3 antibodies (natural antibody); when activated by complement, these antibodies induce intra-or extra-capillary hemolysis [9]. As a matter of course, ribavirin ® was contraindicated in our case. In any event, a similar hemolytic mechanism might have resulted in this patient's production of circulating immune complex and free iron which lodged into his kidney.
HCV-associated glomerulonephritis is characterized by two types of histological changes i.e., membranoproliferative glomerulonephritis and membranous nephropathy (MN) [10,11]. Since the deposition of immunoglobulin and complement is detected on the glomeruli in this condition, these histological changes are thought to be due to immune complex disease [10][11][12]. In our case, proliferative changes were slight, and immunoglobulins and complement breakdown products were found to be deposited primarily in the GBM. Therefore, the primary histological changes in our patient's kidney were classified as being of the MN type. We speculate that glomerular deposition of IC occurred during chronic progression of the disease when the ratio of antigen and antibody was optimized.
There were no direct evidence of a causal relationship between chronic HCV infection and the occurrence of AIHA in our patient, though such a relationship has been suggested in four published reports [13][14][15][16]. Two of four patients that received an orthotopic liver transplant (OLT) were reported to have developed AIHA [13,14]. Though the pathogenesis of AIHA was not discussed in those studies, it may have been related to the strong immunosuppressive therapy that the post-OLT patients received. Another reported case of AIHA was reported in a patient who suffered from B cell chronic lymphocytic leukemia who was being treated with intermittent chemotherapy [15], while still another case was reported in a patient who had a complete congenital deficiency of IgA [16]. Thus, the immune systems of the above four patients were compromised prior to their development of hemolysis. What is not known is how chronic HCV infection leads to AIHA.
The following evidence suggested that this patient's chronic immunological imbalance was triggered by chronic HCV infection. 1) HCV viremia was confirmed. 2) Our patient was of late middle age and this age group was shown to have a high frequency of extra-hepatic manifestations of HCV infection [1,3].
3) It is accepted that the presence of cryoglobulinemia, hypocomplementemia (cold activation), and a biological false positive on the syphilic test are characteristic abnormalities in patients with chronic HCV infection [1,12,17,18]. In just recently paper, Ramos et al. reviewed highly suspected 17 cases with HCV-related AIHA [19]. These authors suggested that a higher prevalence of immunologic markers including cryoglobulinemia and hypocomplementemia all support the hypothesis that HCV-related AIHA has an autoimmune pathogenesis caused by chronic HCV infection.
We concluded that renal involvement in our patient postdated his development of AIHA, which occurred against the backdrop of a progressive autoimmune imbalance induced by chronic HCV infection.