Gluten-sensitive idiopathic neuropathies
|This article relies on references to primary sources. (March 2012)|
Diagnosis of gluten-sensitive neuropathies without a clear cause is on the rise. These idiopathic neuropathies were first identified by screening for anti-gliadin IgG (AGA). The criteria has been critiqued because of the large misdiagnosis rate of coeliac disease (CD), and because AGA exists in the normal population at >12%, far more abundant than cases of neuropathy. The problem in diagnosis arises because there are precursor states prior to coeliac disease. These are called subclinical coeliac disease and early gluten-sensitive enteropathy and are defined as Marsh grade 1 and 2 coeliac disease. Coeliac disease was diagnosed by duodenal biopsy, frequently misinterpreted as negative as high as grade 3 on the Marsh scale. Anti-gliadin antibodies may precede or lag the appearance of coeliac disease. Studies in Scandinavia found an increase of pathologies as much as 10 years in advance of coeliac disease. These included gastrointestinal symptoms, anemia or other autoimmune disease. In addition IgG and IgA responses sometimes accompany allergic responses to proteins. Gliadin is exceptional in that it has several proteins which remain peptides of considerable length after digestion, and migrate into systemic circulation.
There is a controversial subset of people with idiopathic neuropathies and anti-gliadin antibodies that fail to fit all enteropathic criteria except anti-gliadin antibodies. About 1/3 have no DQ2 or DQ8 and an apparent abundance of HLA-DQ1. One percent of coeliacs in Europe have no DQ2 and DQ8 but have DQ1. The DQ1 serotype is very common in the normal population, over 65% of Americans have one copy, therefore the linkage is speculative.
Gluten involvement in idiopathic neuropathies was first defined as neurological dysfunction of an unknown cause associated with increased anti-gliadin antibodies. Early studies primarily focused on "gluten ataxia" and peripheral neuropathies.
A 2008 review concluded "From a purely evidence-based analysis of methodology, it can only be said that it is possible there is an association between coeliac disease or AGA and ataxia, but this association would need to be confirmed by a wide range of investigators doing better designed studies." See also Ataxia (Gluten)
A 2008 literature review concluded that, "based on principles of evidence-based medicine and evaluations of methodology, there is only a 'possible' association [of celiac disease and peripheral neuropathy], due to lower levels of evidence and conflicting evidence. There is not yet convincing evidence of causality."
A 2008 literature review concluded that, "From the evidence-based perspective, there is conflicting evidence whether there is or is not an association between coeliac disease or auto-antibodies and epilepsy. As yet there is no compelling evidence that there is a causal relation. There probably is a specific syndrome—coeliac disease with epilepsy and calcifications—which is rare and perhaps geographically specific."
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- Grossman G (April 2008). "Neurological complications of coeliac disease: what is the evidence?". Pract Neurol 8 (2): 77–89. doi:10.1136/jnnp.2007.139717. PMID 18344378.