Azathioprine (AZA) is used in a wide array of autoimmune diseases, still corresponding to the mainstay maintenance therapy in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides. Although generally well-tolerated, several side effects are recognized. We report the case of a 50-yearold Caucasian man with kidney-limited ANCA myeloperoxidase (MPO) vasculitis who presented with general malaise, fever, worsening renal function, and elevated inflammatory markers 2 weeks after the initiation of therapy with oral AZA. Although a disease relapse was suspected, renal biopsy revealed an eosinophilic infiltrate, suggestive of acute interstitial nephritis. After suspension of AZA, a sustained improvement of renal function and normalization of inflammatory markers was observed. A diagnosis of allergic interstitial nephritis secondary to AZA was established, corresponding to the first biopsy-proven case described in an ANCA MPO vasculitis patient. Although rare, renal toxicity of AZA must be present in the clinician´s mind, avoiding the straightforward assumption of disease relapse in the case of worsening renal function.

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BackgroundSystemic lupus erythematosus (SLE) is a multifaceted autoimmune disease driven by auto-reactive immune cells, in particular B cells that target multiple organ systems leading to severe complications. A main complication of SLE is nephritis, formally known as lupus nephritis (LN). MMF is a selective, non-competitive and reversible inhibitor of inosine monophosphate dehydrogenase. MMF provided to be useful in the treatment of patients affected by SLE, especially in those with LN. MMF demonstrated a more favorable safety profile compared with cyclophosphamide, especially in terms of alopecia and infertility rates. Nonetheless, the use of MMF in LN has not been extensively evaluated in terms of safety and infection rates.ObjectivesTo study the prevalence of infections complications in a cohort of adult LN patients under MMF maintenance therapy.MethodsRetrospective study, enrolling patients attending a Rheumatology/Nephrology department, diagnosed with SLE (American College of Rheumatology criteria) and LN, under MMF maintenance therapy. Drug variables: dose of MMF, time of exposure. Clinical variables: age, gender, race, disease duration, histological classification (renal biopsy), specific organ involvement, other therapeutics for SLE, serum urea and creatinine, 24h proteinuria, and urinary sediment. Statistical analysis with Microsoft Excel 2010; appropriate statistical tests were used; p value<0.05 with a 95% confidence interval will be assumed.Results44 SLE patients were enrolled, 37 were female (84.1%); mean age was 38.4±11.9 years and mean disease duration was 122.9±108 months. All the patients were white. 35 patients (80%) had class 4 LN, 5 had class 5 and histological classification was unknown in 4 patients. 34 (77%) patients had extra renal disease, 23 with joint disease and 14 with cutaneous involvement. Mean MMF dose was 1018±876mg. 35 (79%) patients were doing steroid therapy, mean dose 5.58±3.87mg and 39 (88.6%) patients under Hidroxicloroquine therapy. We identify 25 infectious events, 4 (16%) needing hospitalization, none death. Mean time to infection after MMF introduction was 12.16±16.3 months. The most frequent infections include urinary tract infections (UTI) (8 patients), cutaneous Herpes Zoster (4 patients) and respiratory tract infections (4 patients). We found a positive correlation between the occurrence of infection in the first 8 months of therapy and 24h Proteinúria and dsDNA in the beginning of therapy (p=0.04 and p=0.03, respectively). Hidroxicloroquine seem to have a protective effect against infections, but no statistic association was found. We found no association between infections and MMF/steroid dose or renal function.ConclusionsWe found significant morbidity associated with an increase incidence of infection after introduction of MMF, especially in the first months of therapy and patients with more active disease in the beginning of MMF. No mortality was associated with these infectious complications, and the hospital admission rate was low.ReferencesAfzali B, Shah S, Ch...

Cerebral salt wasting (CSW) is a rare cause of hypoosmolar hyponatremia usually associated with acute intracranial disease characterized by extracellular volume depletion due to inappropriate sodium wasting in the urine. We report a case of a 46-year-old male with recently diagnosed systemic lupus erythematosus (SLE) initially presenting with neurological involvement and an antiphospholipid syndrome (APS) who was admitted because of chronic asymptomatic hyponatremia previously assumed as secondary to syndrome of inappropriate antidiuretic hormone secretion (SIADH). Initial evaluation revealed a hypoosmolar hyponatremia with high urine osmolality and elevated urinary sodium concentration. Clinically, the patient's extracellular volume status was difficult to define accurately. After exclusion of other etiologies, a diagnosis of CSW was established and the patient started appropriate treatment with normalization of sodium levels. The challenge in diagnosing CSW relies on the differentiation from the SIADH, since it shares most of the laboratory features. The critical difference is the state of extracellular volume which can be difficult to access accurately in routine clinical practice. There is evidence that the fractional excretion of urate (FEUrate) can be of assistance. The relationship between SLE and hyponatremia is mostly limited to adverse pharmacological side effects, so to our knowledge, this is the first association between SLE with neurological involvement and CSW.

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