Investigations on the subclinical and clinical nephrotoxicity of interferon alpha-2B in patients with myeloproliferative syndromes

Broad spectrum of interferon-related nephropathies-glomerulonephritis, systemic lupus erythematosus-like syndrome and thrombotic microangiopathy: A case report and review of literature

BACKGROUND

Interferons (IFNs) are characterized by a wide range of biological effects, which justifies their potential therapeutic use in several pathologies, but also elicit a wide array of adverse effects in almost every organ system. Among them, renal involvement is probably one of the most complex to identify.

CASE SUMMARY

We describe four cases of kidney damage caused by different IFN formulations: IFN-β-related thrombotic microangiopathy, IFN-β-induced systemic lupus erythematosus, and two cases of membranous nephropathy secondary to pegylated-IFN-α 2B. In each case, we carefully excluded any other possible cause of renal involvement. Once suspected as the casual relationship between drug and kidney damage, IFN treatment was immediately discontinued. In three cases, we observed a complete and persistent remission of clinical and laboratory abnormalities after IFN withdrawal, while the patient who developed thrombotic microangiopathy, despite IFN withdrawal and complement-inhibitor therapy with eculizumab, showed persistent severe renal failure requiring dialysis.

CONCLUSION

This case series highlights the causal relationship between IFN treatment and different types of renal involvement and enables us to delineate several peculiarities of this association.

Thrombotic microangiopathy induced by interferon beta in patients with multiple sclerosis: three cases treated with eculizumab

BACKGROUND

Interferon-beta (IFN-beta) is one of the most widely prescribed medications for relapsing-remitting multiple sclerosis (RRMS). IFN-related thrombotic microangiopathy (TMA) is a rare but severe complication, with a fulminant clinical onset and a possibly life-threatening outcome that may occur years after a well-tolerated treatment with IFN. Most patients evolve rapidly to advanced chronic kidney disease and eventually to renal failure.

METHODS

We performed a retrospective analysis of TMA cases diagnosed and managed in our Nephrology Department from 2010 to 2015, and performed a literature review of IFN-beta-induced TMA.

RESULTS

Three cases of TMA among patients treated with IFN-beta were identified who did not show any renal improvement following conventional therapy: IFN withdrawal and plasma exchange (PE, range 8-18) sessions. All of them responded favourably to eculizumab, with progressive clinical and renal improvement, allowing dialysis discontinuation, without recurrence of TMA during a long-term follow-up (range 1-5 years).

CONCLUSIONS

TMA is a recognized severe complication in RRMS patients treated with IFN-beta. Withdrawal of IFN and treatment with PE, steroids or rituximab did not improve the poor renal prognosis in our three patients and in all the previously described cases in the literature. In our experience, eculizumab had a strikingly favourable effect on renal recovery, suggesting a role of IFN-beta as a trigger in complement-mediated TMA. Neurologists and nephrologists should be vigilant to this complication to prevent possibly irreversible renal damage.

Emergence of biomarkers in nephropharmacology

Blood-urea nitrogen, serum creatinine and urine output have long been used as markers of kidney function despite their known limitations. In the past few years, a number of novel biomarkers have been identified in the urine and blood that can detect kidney injury early. Although, to date, none of these biomarkers are in clinical use, many have been validated as reliable and sensitive, allowing detection of kidney injury before serum creatinine levels rise and urine output drops. These markers have been evaluated in great detail in animal models and to a lesser extent in humans in postcardiopulmonary bypass and sepsis. There is relatively scarse data on the use of these biomarkers in the detection of kidney injury associated with the use of pharmacologic agents. The purpose of this article is to summarize these data and highlight the potential utility of these biomarkers in nephropharmacology.

Does the antiviral therapy of patients with chronic hepatitis exert nephrotoxic effects?

INTRODUCTION

HBV and HCV chronic hepatitis can be accompanied by secondary renal disease. In addition, these patients receive antiviral drugs with potential nephrotoxicity. It is known that interferon (IFN) therapy in HCV-infected kidney transplant recipients is followed by rejection of the transplant in 50% of the cases. Ribavirin is contraindicated in hemodialyzed patients and in patients with a GFR <50 ml/min/1.73 m(2). IFN therapy requires dosage reduction and close monitoring in patients with a GFR <50 ml/min/1.73 m(2) and in patients with end stage renal disease. The aim of our study was to assess the nephrotoxicity of antiviral drugs in patients with chronic hepatitis by measuring three renal biomarkers: urinary albumin, N-acetyl-β-D-glucosaminidase (NAG) and α 1-microglobulin, as well as glomerular filtration rate (GFR-MDRD4) before and at 6 months of therapy.

METHODS

Fifty-five patients (28 male and 27 female, with a mean age of 47.85 ± 12.03 years) with chronic hepatitis (40 patients with HCV, 13 patients with HBV, 1 patient with HBV+HCV, and 1 patient with HBV+HDV) were enrolled into the study. Different antiviral drug associations were used on a case-by-case basis. The 40 patients with HCV chronic hepatitis received either Peg-IFN-α 2a+Ribavirin (37 patients) or Peg-IFN-α 2b+Ribavirin (3 patients). The 13 patients with HBV chronic hepatitis received Peg-IFN-α 2a (9 patients), Lamivudine (2 patients), Entecavir (1 patient), or Adefovir (1 patient). The patient with HBV+HCV chronic hepatitis received Peg-IFN-α 2a+Ribavirin. The patient with HBV+HDV chronic hepatitis received IFN-α 2a. Urinary albumin (ELISA), NAG (colorimetrical method), α 1-microglobulin (ELISA), and serum creatinine were measured before and at 6 months of antiviral therapy. Urinary markers were expressed as either mg/gCr (for albumin and α 1-microglobulin) or U/gCr (for NAG). Statistical analysis (Pearson's correlation coefficient, paired t-test and χ(2)-test) was performed.

RESULTS

At 6 months of therapy urinary albumin/gCr did not increase significantly: 16.58 ± 23.39 vs. 15.85 ± 24.96 mg/gCr before therapy, p = 0.87. Urinary NAG/gCr did not increase significantly: 4.21 ± 3.37 vs. 3.83 ± 3.2 U/gCr before therapy, p = 0.53. Urinary α 1-microglobulin/gCr was almost unchanged: 4.38 ± 4.47 vs. 4.38 ± 3.57 mg/gCr before therapy, p = 0.99. The GFR did not decline significantly: 92.41 ± 22.21 vs. 94.59 ± 36.1 ml/min/1.73 m(2) before therapy, p = 0.7. Ten patients (18.18%) were albuminuric before therapy, and 14 patients (25.45%) were albuminuric at 6 months of therapy, a non-significant increase (p = 0.35). We found a correlation between urinary albumin/gCr and NAG/gCr and between urinary albumin/gCr and α 1-microglobulin/gCr both at baseline and at 6 months of therapy: r = 0.54, p = 0.0005; r = 0.29, p = 0.03; r = 0.51, p = 0.0005; and r = 0.4, p = 0.002, respectively. In the patient receiving Adefovir, a known nephrotoxic drug, two of the three biomarkers (urinary albumin/gCr and NAG/gCr) increased, most notably NAG/gCr. Both HCV and HBV chronic hepatitis therapy were associated with non-significant changes in renal biomarker excretion and GFR.

CONCLUSIONS

With the exception of Adefovir, all of the drug associations used in this study were safe.

IFN-alpha induces barrier destabilization and apoptosis in renal proximal tubular epithelium

Type I IFNs, like IFN-alpha, are major immune response regulators produced and released by activated macrophages, dendritic cells, and virus-infected cells. Due to their immunomodulatory functions and their ability to induce cell death in tumors and virus-infected cells, they are used therapeutically against cancers, viral infections, and autoimmune diseases. However, little is known about the adverse effects of type I IFNs on nondiseased tissue. This study examined the effects of IFN-alpha on cell death pathways in renal proximal tubular cells. IFN-alpha induced apoptosis in LLC-PK1 cells, characterized by the activation of caspase-3, -8, and -9, DNA fragmentation, and nuclear condensation. IFN-alpha also caused mitochondrial depolarization. Effector caspase activation was dependent on caspase-8 and -9. In addition to apoptosis, IFN-alpha exposure also decreased renal epithelial barrier function, which preceded apoptotic cell death. Caspase inhibition did not influence permeability regulation while significantly attenuating and delaying cell death. These results indicate that IFN-alpha causes programmed cell death in nondiseased renal epithelial cells. IFN-alpha-induced apoptosis is directed by an extrinsic death receptor signaling pathway, amplified by an intrinsic mitochondrial pathway. Caspase-dependent and -independent apoptotic mechanisms are involved. These findings reveal a novel aspect of IFN-alpha actions with implications for normal renal function in immune reactions and during IFN-alpha therapy.

Impaired Filterability of Erythrocytes from Patients with Chronic Hepatitis C and Effects of Eicosapentaenoic Acid on the Filterability

Although erythrocyte filterability plays a key role in microcirculation, it is unknown whether the filterability of erythrocytes from patients with chronic hepatitis C (CH-C) is impaired. This study aimed to investigate erythrocyte filterability in CH-C patients in relation to medical treatment. The mean erythrocyte filterability (%) for all 24 patients with CH-C (69.2 +/- 10.8%) was significantly lower than that for 5 normal controls (80.5 +/- 1.7%, P < 0.03). In 8 patients, the combination therapy of ribavirin (RBV) and interferon improved liver function but caused anemia. The filterability after treatment (57.8 +/- 12.8%) was lower than that before treatment (70.8 +/- 9.7%, P < 0.05). Decreased filterability showed no correlation with the mean corpuscular volume or mean corpuscular Hb concentration during treatment, suggesting that the decrease in filterability mainly arises from changes in erythrocyte membrane properties. We investigated the protective effects of eicosapentaenoic acid (EPA) on the RBV-induced anemia. Filterability in 7 responders was markedly improved from 68.4 +/- 4.6% to 77.4 +/- 2.4% (P < 0.001), but not in 3 nonresponders. In the responders, the progression of anemia was restrained. In conclusion, we found an obvious impairment of the filterability of erythrocytes from CH-C patients, further impairment of the filterability induced by oxidative membrane damage caused by RBV leading to hemolytic anemia, and amelioration of the filterability caused by the antioxidative effects of EPA.

Traitements complémentaires de l’hépatite chronique virale C

Pegylated interferon and ribavirin combination therapy represent the standard-of-care treatment for chronic hepatitis C, that allows to cure more than half of the patients. However, the success of this bitherapy is in balance with numerous side effects, especially hematologic and psychiatric. This review is focused on complementary treatments (erythropoietin, G-CSF, vitamin E, glutathion, ursodeoxycholic acid and antidepressants) likely to bring a benefit in maintaining adequate interferon and ribavirin dosages and in improving quality of life. This analysis has been performed by using the Medline(R) data base and with data from laboratories which commercialized these molecules. Erythropoietin, G-CSF and antidepressants are the best tools to optimize the bitherapy in its dose and its duration while privileging the quality of life of HCV-infected patients.

Hematologic side effects of interferon and ribavirin therapy

Pegylated (PEG)-interferon and ribavirin combination therapy are the standard of care for the treatment of chronic hepatitis C and are associated with a high rate of sustained virologic response. However, there is a high incidence of hematologic side effects with this therapeutic regimen. Hematologic side effects are particularly common; bone marrow suppression caused by interferon may result in neutropenia and thrombocytopenia. Ribavirin is directly toxic to red blood cells and is associated with hemolysis, which is usually dose-related but self-limited. Historically, the traditional management of hematologic side effects of interferon therapy has been dose reduction. However, recent studies have shown that response to therapy is strongly influenced by adherence to optimal doses of interferon and particularly ribavirin. Therefore, there is increasing emphasis on the use of growth factors such as filgrastim and erythropoietin to stimulate bone marrow production of erythrocytes and leukocytes to allow patients to receive the optimal doses of interferon and ribavirin. The incidence, magnitude, and possible mechanisms of hematologic complications associated with interferon and ribavirin are described in this review.

Hematologic disorders associated with hepatitis C virus infection and their management

More than 4 million people in the United States are infected with hepatitis C virus (HCV). During the next 20-30 years, the burden of HCV-related mortality and morbidity will likely double. To date, the most effective treatment for chronic HCV infection is the combination of either interferon (IFN)-alpha or pegylated IFN-alpha and ribavirin. For a sustained virologic response, treatment adherence and dose maintenance are essential. However, both IFN-alpha and ribavirin induce hematologic toxicity, such as anemia, neutropenia, and thrombocytopenia, which can compromise treatment adherence and dose maintenance and could, therefore, potentially influence outcomes. Although there are currently no approved treatments for hematologic complications of HCV therapy, studies have shown that hematopoietic growth factors can provide significant benefits. This review highlights the pharmacology, risks, and benefits of recombinant hematopoietic growth factor therapy in HCV-infected patients.

Essential thrombocythemia (ET): moving from palliation to cure

Essential thrombocythemia (ET) is a clonal hematopoietic stem cell myeloproliferative disorder characterized by megakaryocytic hyperplasia and persistent thrombocytosis. The clinical presentation and evolution of ET are heterogeneous. This review highlights the current treatment options in the management of ET, including hydroxyurea, anagrelide and both regular and pegylated interferons. Anagrelide, while very effective at controlling counts and symptoms in most patients, may not consistently reduce the bone marrow megakaryocyte mass. Interferon is very effective and not associated with leukemogenesis, but has not been proven to restore polyclonal hematopoiesis and has significant dose-related adverse events. Pegylated interferon represents a significant improvement over the unmodified interferon preparations. Novel therapeutic options directed towards eradication of the malignant ET clone are required.

Alpha-interferon therapy induces improvement of platelet counts in children with chronic idiopathic thrombocytopenic purpura

PURPOSE

To investigate alpha-interferon (IFN) therapy for children with chronic idiopathic thrombocytopenic purpura (ITP).

PATIENTS AND METHODS

Patients with refractory ITP lasting more than 12 months from diagnosis were included if they had platelet counts <50 x 10(9)/L and had received no treatment during the past month. Patients received IFN (3 x 10(6) U/m2 per dose), three times per week for 4 weeks; if partial (<150 x 10(9)/L) or no response was obtained, the same dose was continued for another 8 weeks. In patients with favorable response and subsequent decrease to pre-treatment values, an additional 4 weeks of treatment could be administered.

RESULTS

Fourteen patients (ages 4-20 y) receiving 17 IFN courses were included. Mean initial platelet count was 29 +/- 15 x 10(9)/L. A significant increase was achieved during 14 of 17 courses (82.4%). All but two responses were transitory, and platelets returned to initial values after IFN discontinuation (mean 44 +/- 26 days). Considering the best response achieved by each patient, we observed: 1) 10 patients who achieved a sustained improvement of platelet count throughout the treatment period, decreasing to initial values after therapy was stopped; 2) one patient who achieved platelet count >150 x 10(9)/L, remaining with normal platelets at 18 months; 3) one patient who achieved platelet count >150 x 10(9)/L, remaining with platelets between 100 and 140 x 10(9)/L at 48 months; 4) one patient who had no response; and 5) one patient in whom therapy worsened the thrombocytopenia. A mild to moderate flu-like syndrome and a moderate decrease of the absolute neutrophil count were the only side effects observed.

CONCLUSION

Interferon therapy induces a significant increase of platelet count and seems to be a valid alternative therapy to attempt the achievement of prolonged remission in refractory ITP, to defer splenectomy in younger children, or to improve platelet count before planned splenectomy.

Anticancer drug-induced kidney disorders

Nephrotoxicity is an inherent adverse effect of certain anticancer drugs. Renal dysfunction can be categorised as prerenal uraemia, intrinsic damage or postrenal uraemia according to the underlying pathophysiological process. Renal hypoperfusion promulgates prerenal uraemia. Intrinsic renal damage results from prolonged hypoperfusion, exposure to exogenous or endogenous nephrotoxins, renotubular precipitation of xenobiotics or endogenous compounds, renovascular obstruction, glomerular disease, renal microvascular damage or disease, and tubulointerstitial damage or disease. Postrenal uraemia is a consequence of clinically significant urinary tract obstruction. Clinical signs of nephrotoxicity and methods used to assess renal function are discussed. Mechanisms of chemotherapy-induced renal dysfunction generally include damage to vasculature or structures of the kidneys, haemolytic uraemic syndrome and prerenal perfusion deficits. Patients with cancer are frequently at risk of renal impairment secondary to disease-related and iatrogenic causes. This article reviews the incidence, presentation, prevention and management of anticancer drug-induced renal dysfunction. Dose-related nephrotoxicity subsequent to administration of certain chloroethylnitrosourea compounds (carmustine, semustine and streptozocin) is commonly heralded by increased serum creatinine levels, uraemia and proteinuria. Additional signs of streptozocin-induced nephrotoxicity include hypophosphataemia, hypokalaemia, hypouricaemia, renal tubular acidosis, glucosuria, aceturia and aminoaciduria. Cisplatin and carboplatin cause dose-related renal dysfunction. In addition to increased serum creatinine levels and uraemia, electrolyte abnormalities, such as hypomagnesaemia and hypokalaemia, are commonly reported adverse effects. Rarely, cisplatin has been implicated as the underlying cause of haemolytic uraemic syndrome. Pharmaceutical antidotes to cisplatin-induced nephrotoxicity include amifostine, sodium thiosulfate and diethyldithiocarbamate. Dose- and age-related proximal tubular damage is an adverse effect of ifosfamide. In addition to renal wasting of electrolytes, glucose and amino acids, Fanconi syndrome, rickets and osteomalacia have occurred with ifosfamide treatment. High dose azacitidine causes renal dysfunction manifested by tubular acidosis, polyuria and increased urinary excretion of electrolytes, glucose and amino acids. Haemolytic uraemia is a rare adverse effect of gemcitabine. Methotrexate can cause increased serum creatinine levels, uraemia and haematuria. Acute renal failure is reported following administration of high dose methotrexate. Urinary alkalisation and hydration confer protection against methotrexate-induced renal dysfunction. Dose-related nephrotoxicity, including acute renal failure, are reported subsequent to treatment with pentostatin and diaziquone. Acute renal failure is a rare adverse effect of treatment with interferon-alpha. Haemolytic uraemic syndrome occurs with mitomycin administration. A mortality rate of 50 to 100% is reported in patients developing mitomycin-induced haemolytic uraemic syndrome. Capillary leak syndrome occurring with aldesleukin therapy can cause renal dysfunction. Infusion-related hypotension during infusion of high dose carmustine can precipitate renal dysfunction.

Local cutaneous necrotizing lesions associated with interferon injections

Long-term i.m. or s.c. injections of interferon-alpha, beta, and gamma(IFN) in patients with chronic myelogenous leukemia (CML) can cause severe, long-lasting cutaneous complications consistent with necrotizing vasculitis. The purpose of this study was to describe the cutaneous lesions and the course of illness in 7 well-documented patients with Philadelphia chromosome-positive (Ph+) CML treated with IFN. We reviewed 7 patients diagnosed with Ph+ CML at M.D. Anderson Cancer Center between 1983 and 1994 who experienced cutaneous lesions at the injection site after treatment with i.m. or s.c. IFN (3 patients treated with IFN-alpha, 3 with combined IFN-alpha and IFN-gamma, and 1 with IFN-beta). According to pathology reports available for 3 patients, the cutaneous lesions seem to be consistent with necrotizing vasculitis. The skin reactions occurred independent of the IFN type, administration modality (i.m. or s.c.), duration of previously received IFN therapy (3-108 months), stage of disease, and cytogenetic response to IFN treatment. Of 7 patients, 4 developed low-grade fever during the occurrence of skin reactions, but all cultures taken from the abscesslike lesions were negative for bacterial or fungal infection. These lesions either did not resolve and required surgical debridement (5 patients) or resolved slowly with conservative management that included discontinuation of IFN at the specific, involved site. Independent of the IFN type or i.m. or s.c. injections, IFN can cause painful and long-lasting cutaneous lesions that frequently require surgical intervention. Whether this is a result of the high concentration of IFN at the injection site, the diluent, or an immunologic reaction remains unclear.

The role of alpha-interferon in essential thrombocythaemia, polycythaemia vera and myelofibrosis with myeloid metaplasia (MMM): a concise update

Treatment of essential thrombocythaemia (ET), polycythaemia vera (PV), and myelofibrosis with myeloid metaplasia (MMM) patients is frequently a difficult issue. To date, there is no generally accepted treatment for these diseases which can reduce the risk of thromboembolism and/or haemorrhagic events, avoid any increase in the frequency of secondary myelofibrosis and terminal blast transformation and decrease the reticulin content in the bone marrow of MMM patients. The most frequently used myelosuppressive agent is hydroxyurea (HU), but widespread application has failed to demonstrate that is not leukaemogenic. In patients with MMM, conflicting results have been obtained following alpha-IFN treatment. Haematological responses have been seen in 50% of the patients. Usually the patients showing good responses had a hyperproliferative type of disease. In only one case was a reduction of reticulin content of the bone marrow observed. Thus, these findings do not indicate alpha-IFN as a first-line therapy. On the other hand, the results of several reports in ET and PV patients have shown a reduction in the abnormal proliferation of megakaryocytes and erythroid elements, following alpha-IFN treatment. A reduction in spleen size has also frequently been seen. Together with the improvement of haematological parameters, clinical symptoms have also responded positively. Long term control of these diseases can be obtained with a well-tolerated low dose of alpha-IFN. However, PV and ET are not usually characterized by cytogenetic abnormalities, making it very difficult to demonstrate the disappearance of clonal haemopoiesis following alpha-IFN therapy, even if this does occasionally occur, as evident from the two cytogenetic convertions described in the literature. As compared to myelosuppressive drugs or phlebotomy, alpha-IFN thus represents an attractive new treatment, able to exert a fundamental influence on these diseases, presumably without any untoward leukaemogenic or gonadotoxic activity.

[Nephropathies caused by interferon alpha: apropos of 2 cases]

Two cases reports of interferon alpha-associated nephropathy are reported. The first observation is a membranoproliferative glomerulonephritis and the second a renal microangiopathy. The different cases in the literature are reviewed and the pathophysiology is discussed.

Clinical toxicity of the interferons

Since their initial description in 1957, the interferons (IFNs) have been increasingly used to treat a wide array of diseases. Acute adverse effects, i.e. 'flu-like' syndromes, hypo- or hypertension, tachycardia, headache, myalgias and gastrointestinal disorders, occur within the first hour or day after starting treatment. They are seldom treatment-limiting and are easily manageable. Sub-acute and chronic effects develop after several days, usually within 2 and 4 weeks of therapy. The most typical is neurological toxicity, including fatigue/asthenia, and behavioural and cognitive changes. Such symptoms may seriously impair quality of life and result in treatment discontinuation. Seizures have seldom been described. Other infrequent central nervous system adverse effects include vertigo, cramp and oculomotor nerve paralysis. Distal paraesthesias and peripheral neuropathy have been reported. IFN-associated autoimmunity is quite rare but a matter of concern. Biological or clinical manifestations usually require several months to become apparent. Autoantibodies have been shown to develop in most patients but have been inconsistently associated with clinical symptoms of systemic lupus erythematosus, rheumatoid-like arthritis and thyroiditis. Both hypo- and hyperthyroidism have been described but are usually reversible. Other infrequent autoimmune reactions include diabetes, pemphigus and worsening of multiple sclerosis. Although several patients present with a pre-existing autoimmune disorder, no predisposing factor has been clearly established. While hypotension and tachycardia are the most frequent acute cardiovascular complications, a few additional cases of cardiac arrhythmias and myocardial ischaemia have been reported after a short course or several weeks of treatment. These latter complications do not appear to be dose-dependent or age-related. Isolated cases of congestive heart failure have also been described. Mild proteinuria has been observed in 15 to 25% of patients, but acute renal toxicity is uncommon. A transient rise in serum aminotransferase levels is frequently noted during the first stage of therapy, especially in patients receiving the highest dosages. Direct hepatotoxicity is extremely rare. Autoimmune hepatitis, which is ill-diagnosed as chronic viral hepatitis, and de novo induction of autoimmune hepatitis, account for the majority of liver diseases. Haematotoxicity is relatively common but mild to moderate, and develops gradually during the first weeks of treatment. Neutropenia is the most common haematological toxicity, but is usually not dose-limiting and resolves rapidly upon drug discontinuation. Myelosuppression, autoimmune and immune allergic haemolytic anaemias and thrombocytopenias have seldom been described. Cutaneous adverse effects comprised nonspecific erythema and hair loss and, less frequently, vasculitis, local ulcerations at the site of injection and exacerbation of psoriasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemolytic-uremic syndrome during recombinant alpha-interferon treatment for hairy cell leukemia

We report a case of hemolytic uremic syndrome in a patient suffering from hairy cell leukemia during recombinant alpha-interferon treatment. We believe that this is the first report of the occurrence of this peculiar kind of acute renal failure following alpha-interferon therapy. This association may suggest possible speculations regarding side effects of interferon treatment and pathogenesis of hemolytic uremic syndrome.