Increased risk of IgA nephropathy among individuals with celiac disease

Gluten and IgA nephropathy: you are what you eat?

Although extensively studied, the relationship between dietary antigens-in particular, gluten-and IgA nephropathy remains unclear. Using a double transgenic mouse model of IgA nephropathy that expresses both human IgA1 and human CD89, Papista et al. report that a gluten-free diet protects against the development of IgA deposition and glomerular injury, and that these events occur with the introduction of dietary gluten.

The mucosa-kidney axis in IgA nephropathy

Links between IgA nephropathy (IgAN) and the mucosa have been recognized since the 1970s. In particular, the observation of visible haematuria induced by respiratory infections in patients with IgAN and the association of IgAN with diseases in which the mucosa plays a part, especially coeliac disease, have been taken as evidence of a mucosa-kidney axis. Here, we review current evidence that links the mucosa, in particular the gastrointestinal mucosa, and IgA produced by the bone marrow with IgAN. Genome-wide association studies in patients with IgAN have identified risk loci in genes involved in the intestinal mucosal integrity and immune network. Furthermore, the systemic immune response to mucosal antigens in IgAN is increased. Moreover, patients with IgAN have an increased reactivity to dietary proteins associated with subclinical intestinal mucosal inflammation. Associations between IgAN and gastrointestinal diseases have also been reported in a small number of patients, but whether these diseases share a common pathogenesis or whether gastrointestinal inflammation exacerbates IgAN is uncertain. Indeed, mucosal alterations such as infections could activate the innate immune system, aggravate a pre-existing IgAN and promote disease manifestations such as macrohaematuria. Various clinical interventions and trials targeting the mucosa or presumed mucosa-associated mechanisms have so far not yielded consistent findings and the results of ongoing trials are eagerly awaited.

Relevance, pathogenesis and clinical implications of thyroid disorders in children with celiac disease

Celiac disease is a frequent chronic inflammatory small bowel disease which may present itself with associated autoimmune comorbidities. Among these comorbidities, thyroid disorders show a significant prevalence; even in the pediatric population. However, the exact epidemiology and clinical significance of such alterations are yet to be fully elucidated. The most updated guidelines do not currently offer any specific support. Focusing on the pediatric population, we will review the recent available literature that we believe might be helpful in advancing the clinician's knowledge-base regarding this issue. We also discuss which, to our knowledge, are the key pathophysiologic concepts behind the association between these two entities. Finally, we offer our own clinical perspective, recommending routine laboratory thyroid screening, possibly followed by an echographic thyroid evaluation as we believe such an approach to be appropriate when caring for children with celiac disease.

The Spectrum of Differences between Childhood and Adulthood Celiac Disease

An old saying states that ''children are not little adults" and this certainly holds true for celiac disease, as there are many peculiar aspects regarding its epidemiology, diagnosis, clinical presentations, associated diseases, and response to treatment in pediatric compared to adult populations, to such an extent that it merits a description of its own. In fact, contrary to the past when it was thought that celiac disease was a disorder predominantly affecting childhood and characterized by a malabsorption syndrome, nowadays it is well recognized that it affects also adult and elderly people with an impressive variability of clinical presentation. In general, the clinical guidelines for diagnosis recommend starting with specific serologic testing in all suspected subjects, including those suffering from extraintestinal related conditions, and performing upper endoscopy with appropriate biopsy sampling of duodenal mucosa in case of positivity. The latter may be omitted in young patients showing high titers of anti-transglutaminase antibodies. The subsequent management of a celiac patient differs substantially depending on the age at diagnosis and should be based on the important consideration that this is a lifelong condition.

Mapping novel immunogenic epitopes in IgA nephropathy

BACKGROUND AND OBJECTIVES

IgA plays a key role in IgA nephropathy (IgAN) by forming immune complexes and depositing in the glomeruli, leading to an inflammatory response. However, the antigenic targets and functional characterization of IgA have been incompletely defined in this disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study was performed in sera from patients who were studied as part of a prospective, observational study of IgAN. These patients (n=22) all had biopsy-proven IgAN within 3 years of study initiation, complete clinical data, annual urinary inulin clearance for GFRs, and at least 5 years of follow-up. Progression was defined as loss of >5 ml/min per 1.73 m(2) per year of inulin clearance measured over at least 5 years. A protein microarray was used for detection of IgAN-specific IgA autoantibodies in blood across approximately 9000 human antigens to specifically identify the most immunogenic protein targets that drive IgA antibodies in IgAN (n=22), healthy controls (n=10), and non-IgAN glomerular diseases (n=17). Results were validated by ELISA assays in sera and by immunohistochemistry in IgAN kidney biopsies. IgA-specific antibodies were correlated with clinical and histologic variables to assess their effect on disease progression and prognosis.

RESULTS

Fifty-four proteins mounted highly significant IgA antibody responses in patients with IgAN with a false discovery rate (q value) of ≤10%; 325 antibodies (P≤0.05) were increased overall. Antitissue transglutaminase IgA was significantly elevated in IgAN (P<0.001, q value of 0%). IgA antibodies to DDX4 (r=-0.55, P=0.01) and ZADH2 (r=-0.48, P=0.02) were significantly correlated with the decline of renal function. Specific IgA autoantibodies are elevated in IgAN compared with normal participants and those with other glomerular diseases.

CONCLUSIONS

In this preliminary study, IgA autoantibodies target novel proteins, highly expressed in the kidney glomerulus and tubules. These IgA autoantibodies may play important roles in the pathogenesis of IgAN.

Prevalence of celiac disease in cirrhosis and outcome of cirrhosis on a gluten free diet: a prospective study

BACKGROUND & AIMS

Current consensus suggests CD to be a multi-systemic disease that could affect any organ system including the liver. It remains under-diagnosed in the US and its prevalence and management in cirrhotic patients has not been studied. Our aim was (1) to estimate the prevalence of CD in cirrhosis, (2) to characterize cirrhotic patients with abnormal celiac serology and normal small bowel biopsy and (3) to evaluate the effect of a GFD on the liver.

METHODS

A total of 204 consecutive patients with biopsy proven cirrhosis scheduled for an upper endoscopy (EGD) to assess and treat gastro-esophageal varices (GEV) at the Cleveland Clinic between 5/1/2008 and 5/30/2010 were enrolled in the study and followed for 2 years.

RESULTS

CD affects 2.5% of cirrhotic patients and more than twice the prevalence in the general population. Abnormal EMA >1/10 and high hTTG levels >20 IU can be used to diagnose CD in cirrhosis. Sensitivities and specificities are 100% for EMA and 80% and 94% for hTTG, respectively. After a GFD, patients with CD showed a return to normal levels of their celiac serology, small bowel biopsy and liver enzyme abnormalities.

CONCLUSIONS

CD is at least twice more common in cirrhotic patients than in the general population and GFD improves liver tests. CD can occur coincidentally with other liver disorders and screening may be warranted during the evaluation of patients with cirrhosis. Abnormal EMA and high hTTG levels can be used to diagnose CD in cirrhosis.

Lack of serologic evidence to link IgA nephropathy with celiac disease or immune reactivity to gluten

IgA nephropathy is the most common form of primary glomerulonephritis worldwide. Mucosal infections and food antigens, including wheat gluten, have been proposed as potential contributing environmental factors. Increased immune reactivity to gluten and/or association with celiac disease, an autoimmune disorder triggered by ingestion of gluten, have been reported in IgA nephropathy. However, studies are inconsistent about this association. We aimed to evaluate the proposed link between IgA nephropathy and celiac disease or immune reactivity to gluten by conducting a comprehensive analysis of associated serologic markers in cohorts of well-characterized patients and controls. Study participants included patients with biopsy-proven IgA nephropathy (n = 99), unaffected controls of similar age, gender, and race (n = 96), and patients with biopsy-proven celiac disease (n = 30). All serum specimens were tested for IgG and IgA antibodies to native gliadin and deamidated gliadin, as well as IgA antibody to transglutaminase 2 (TG2). Anti-TG2 antibody-positive nephropathy patients and unaffected controls were subsequently tested for IgA anti-endomysial antibody and genotyped for celiac disease-associated HLA-DQ2 and -DQ8 alleles. In comparison to unaffected controls, there was not a statistically significant increase in IgA or IgG antibody reactivity to gliadin in individuals with IgA nephropathy. In addition, the levels of celiac disease-specific serologic markers, i.e., antibodies to deamidated gliadin and TG2, did not differ between IgA nephropathy patients and unaffected controls. Results of the additional anti-endomysial antibody testing and HLA genotyping were corroborative. The data from this case-control study do not reveal any evidence to suggest a significant role for celiac disease or immune reactivity to gluten in IgA nephropathy.