Autistic enterocolitis

Overview
Autistic enterocolitis is a controversial term first used by British gastroenterologist Andrew Wakefield to describe a number of common clinical symptoms and signs which he contends are distinctive to autism. The existence of autistic enterocolitis is controversial, as the methodology of Wakefield's studies has been criticized and his results have not been replicated by other groups.

Background
Until the 1970s, autism was considered a very rare condition, but it is diagnosed much more often nowadays, whether due to increased diagnostic vigilance by doctors, changes of diagnostic categories, or an actual increase in incidence. Late-onset autism cases are estimated at 25% and reported by sources including the British Medical Journal as not having changed in recent years. Wakefield, however, contends that a regressive syndrome "may reflect a subset of children with developmental disorders with distinct etiological and clinical features."

Despite others describing common bowel features, there have been no peer reviewed studies yet published, as of 2006, corroborating the existence of autistic enterocolitis; other studies have explicitly denied its existence. Thus, it is not generally accepted that the types of colitis found in autism are unique to autism. To date, no adequately controlled study has been published comparing the gut pathology of autistic and non-autistic children.

Lancet study
When Wakefield and his colleagues first reported in 1998 a possible association between autistic regression, IBD, and MMR vaccines in the Lancet, they evaluated a dozen children with pervasive developmental disorders, apparent developmental regression, and intestinal symptoms, referred to the Royal Free Hospital.

According to parents, onset of behavioral symptoms was linked to recent (within two weeks) immunization with MMR vaccine in eight of the children diagnosed with developmental disorders. The most consistent report was lymphoid nodular hyperplasia of the terminal ileum in nine of the children. This feature has also been reported to be very common in non-autistic children. A variety of colonic and rectal mucosal features was reported in eight cases. Biopsies of the ileum was reported to have shown reactive lymphoid follicular hyperplasia in seven. Biopsies of the colon was reported to have shown a diffuse mononuclear cell infiltrate in six.

Wakefield and his colleagues say they have described features of regressive autistism with bowel disorders, or what Wakefield would later call autistic enterocolitis, although these findings have been questioned, with claims that the association of features is substantially an artifact of preselection of vaccinated children with both developmental disorders and bowel symptoms for a UK lawsuit:
 * Most of the children were reported to have swelling of the lymphoid tissue lining the intestines, particularly near where the small and large intestines meet, and inflammation of the large intestine, associated with constipation, diarrhea and, in some cases, pain.
 * In some affected children, impaired cellular immunity to common recall antigens, with low numbers of circulating white blood cells were reported.
 * A specific measles protein signal is claimed to have been detected in inflamed lymphoid tissue.
 * In some cases, loss of speech and language, bowel disturbances, self-injury, and a self-limited diet, associated with cravings for particular foods.
 * Allergies, food intolerances are also reported in some children.

IBD and regressive autism
Although also characterized by intestinal lymphoid tissue disease activity, the primary symptoms and diagnostic criteria of the syndrome are claimed to be behavioral and developmental. Age, dose of infection and the interaction of two or more viruses are claimed to be factors leading to regressive autism. According to Wakefield, "it is possible that the emergence of this new type of autism is related to a different pattern of exposure to environmental triggers."

Abnormal metabolites of macro-nutriments are claimed to have been found in the urine of some autistic children, suggesting an incomplete or insufficient intra-intestinal digestion.

Supposed link to MMR vaccinations
Central to one of the most acrimonious controversies in autism, Wakefield has hypothesized that autistic enterocolitis is an emergent IBD phenotype that follows from exposure ro the vaccinations given to children during a period when their immune systems are rapidly developing. Specifically, Wakefield asserts the autistic enterocolitis syndrome involves increased permeation of neurotoxic substances across the blood-brain barrier during a vulnerable part of brain development, leading to regressive autism.

Other research, however, rejects this hypothesis, and other groups have not reproduced Wakefield's findings. Researchers have identified a high incidence of bowel symptoms in autistic children before the MMR vaccine was licensed. It was also revealed that, prior to the publication of Wakefield's studies alleging a connection between the MMR vaccine and autistic enterocolitis, he had received over £400,000 from lawyers attempting to sue vaccine manufacturers. This conflict of interest, which Wakefield denies, has led many to criticize Wakefield and his results. The British General Medical Council has launched an inquiry into possible dishonesty by Wakefield regarding his research.

"Retraction of an interpretation"
The Lancet paper has been widely cited as an impetus for concerns regarding the MMR vaccine being a cause of Autism. Wakefield gave interviews after the publication of the paper, including on 60 Minutes where he raised concerns regarding administraiton of the MMR vaccine. In the Lancet paper, Wakefield and his co-authors said on the issue:
 * "We did not prove an association between measles, mumps, and rubella vaccine and the syndrome described. Virological studies are underway that may help to resolve this issue"

In 2004, 10 of the 13 authors issued a statement in the Lancet entitled "Retraction of an interpretation". In this, the authors retracted the conclusion section of the paper, formally known in the Lancet and in many biomedical journals, as the "interpretation". The section of the paper retracted said:


 * "Interpretation. We identified associated gastrointestinal disease and developmental regression in a group of previously normal children, which was generally associated in time with possible environmental triggers."

In the retraction, issued in March 2004, they said:


 * "We wish to make it clear that in this paper no causal link was established between MMR vaccine and autism as the data were insufficient. However, the possibility of such a link was raised and consequent events have had major implications for public health. In view of this, we consider now is the appropriate time that we should together formally retract the interpretation placed upon these findings in the paper, according to precedent."

The authors also said:


 * "The main thrust of this paper was the first description of an unexpected intestinal lesion in the children reported. Further evidence has been forthcoming in studies from the Royal Free Centre for Paediatric Gastroenterology and other groups to support and extend these findings. While much uncertainty remains about the nature of these changes, we believe it important that such work continues, as autistic children can potentially be helped by recognition and treatment of gastrointestinal problems."

Just before the retraction, criticism arose over the fact that the Royal Free Hospital had received £55 000,00 in August 1996 from lawyers preparing to sue MMR manufacturers for support of Dr. Wakefield's research. Wakefield asserted that the donation was to fund a second clinical study; some of the children involved were subjects in both studies. However, it was subsequently revealed by The Sunday Times of London that Wakefield had personally been paid more than £400,000.

Wakefield, who did not sign the retraction, currently face disciplinary charges before the General Medical Council over the conduct of this research. In October 2005, the Cochrane Library published its analysis of 31 "high quality" medical studies which concluded no link could be found between the MMR vaccine and bowel disease, autism or other pervasive developmental disorders. To increase the rigor of the meta-analysis, the criteria of the meta-analysis excluded smaller studies and studies that had the potential for bias. Wakefield's work was specifically excluded in the meta-analysis due to small sample size. With regard to the vaccine, Cochrane said that its survey of research "strongly supports its use."