Prevalence rates suggest that autoimmune disease (AD) is not uncommon, affecting approximately 5% of women in the U.S. and 3% of men (
Cooper & Stroehla, 2003). Rose and Bona propose three types of evidence that establish an autoimmune disease: direct evidence from transfer of pathogenic antibody or pathogenic T cells, indirect evidence based on reproduction of the autoimmune disease in experimental animals, and circumstantial evidence from clinical clues (
Rose & Bona, 1993).
One line of clinical support has developed from a purported link between parental AD and developmental/neurobiological disorders in children. Findings remain equivocal. In one noteworthy study, investigators compared families that had a child with Pervasive Developmental Disorder (PDD) to those that had a child with an autoimmune disease and those with a healthy child, and found that families of a child with PDD had a higher frequency of autoimmune diseases (especially Rheumatic Fever) than did either other family type (
Sweeten, Bowyer, Posey, Halberstadt, & McDougle, 2003). Another study did not find a significant difference in general prevalence of maternal autoimmune disease (between youth with autism and normal controls), but did report both an association between infantile autism and maternal ulcerative colitis in a sample of 111 patient-mother pairs (as compared to 330 control pairs); and between infantile autism and paternal type I diabetes (
Mouridsen, Rich, Isager, & Nedergaard, 2007). Finally, Croen and colleagues did not find a significant difference in general prevalence of maternal autoimmune disease (based upon children’s PDD caseness) (
Croen, Grether, Yoshida, Odouli, & Van de Water, 2005); however, psoriasis did occur more frequently among those mothers of children with autism than among those of children without the diagnosis. As the incidence of autoimmune diseases increases throughout adult life, and this latter study only took into account maternal autoimmune conditions diagnosed within the 4-year period surrounding childbirth, a longer-term study would clearly be warranted.
Autoimmune and genetic contributions have been purported in bipolar disorder as well. Vonk et al. sampled thyroperoxidase antibodies (TPO-Abs) in 22 monozygotic and 29 dizygotic bipolar twins as well as 35 healthy control twins (
Vonk, van der Schot, Kahn, Nolen, & Drexhage, 2007). Twenty-seven percent of subjects with bipolar disorder were positive for autoimmune thyroiditis, while only 16% of the control subjects tested positive. Further, there were significant differences in TPO-Abs such that monozygotic non-bipolar co-twins had the highest levels; followed by significantly lower levels in dizygotic non-bipolar co-twins; and, lastly, by significantly lower levels still in control twins. While the TPO-Abs levels in bipolar patients were significantly higher than in controls, levels did not differ between those with bipolar disorder and their non-bipolar twins, suggesting that increased TPO-Abs levels may be more related to genetic vulnerability to develop the disease than to the disease process (
Vonk, et al., 2007).
The potential autoimmune contribution to Tourette Syndrome (TS) has recently gained research attention. For instance, although the sample size was modest, Yeh et al. found antineural antibodies in the sera of four patients with TS as well as in their family members (
Yeh, et al., 2006); in contrast, antineural antibodies were not found in normal healthy controls. This presumed link between autoimmune processes and certain mental disorders has also sparked the study of neuroimmunological processes as they potentially relate to the pathophysiology of obsessive compulsive disorder (OCD). Indeed, the finding of anti-brain antibodies in patients with OCD offers circumstantial evidence for central nervous system (CNS) autoimmunity (
Murphy, Sajid, & Goodman, 2006). Also pointing to a link, patients with Sydenham’s chorea (SC), systemic lupus erythromatosus, and other autoimmune diseases have evidenced a high rate of comorbid OCD (
Murphy, et al., 2006;
Slattery, et al., 2004). In fact, relative to the general population, individuals with systemic lupus erythromatosus are 10 to 15 times more likely to have OCD (
Bachen, Chesney, & Criswell, 2009;
Slattery, et al., 2004). Further, OCD was more prevalent among relatives of subjects with Rheumatic Fever (RF) than among control relatives – even when RF-affected relatives were taken out of the analyses (
Hounie, et al., 2007) – suggesting that psychiatric disorders are associated with autoimmune disease in both affected patients and their relatives.
Rheumatic Fever is a classic example of an autoimmune illness triggered by an infection. With RF, the pathogen involved is group A streptococcus (GAS), the most common cause of childhood bacterial pharyngitis (
Cunningham, 2000). GAS infections have been implicated to trigger pediatric onset neuropsychiatric disorders, most notably OCD and tic disorders. This presentation of OCD and tic disorders with presumed association to GAS infection has been collectively categorized as Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus (PANDAS) (
Murphy, et al., 2004;
Swedo, et al., 1998). As yet, PANDAS has not been universally accepted as an official diagnosis, nor is it clear what features will clearly delineate this subtype from other youth with tics and OCD. For example; in an examination of rates of neuropsychiatric disorders in 139 first degree relative (FDR) of 54 subjects with PANDAS, 26% of PANDAS subjects had a FDR with OCD. While this rate is significantly higher than the general population, it is similar to that reported for subjects with OCD and tic disorders (
Lougee, Perlmutter, Nicolson, Garvey, & Swedo, 2000). This study did not report rates of autoimmunity in FDR.
Although a causal relationship between streptococcus and both OCD and tic disorders has yet to be determined, mounting evidence suggests immune dysfunction in a subset of patients with OCD and tics (
Dale, Heyman, Giovannoni, & Church, 2005;
Hoekstra & Minderaa, 2005;
Maina, et al., 2009;
Morer, et al., 2008); as well as neuropsychiatric risks from repeated streptococcal infections (
Mell, Davis, & Owens, 2005;
Murphy, et al., 2006;
Perrin, et al., 2004). The underlying pathophysiology is not known. Maternal antibodies are transferred during pregnancy (
Lee, et al., 2009); but some have postulated this transplacental passage of antibodies may affect brain development via inflammation or via interaction with neurotransmitter receptors (
Vincent, Dalton, Clover, Palace, & Lang, 2003). Circumstantial evidence for autoimmunity includes environmental triggers of relapses, familial risk, and response to immune modulating therapies (
Murphy, Sajid, & Goodman, 2006). Recreating the illness either by animal models via recreation of autoimmune pathology or by passive transfer of antibodies has been mixed (
Loiselle, Lee, Moran, & Singer, 2004;
Yaddanapudi, et al., 2009). In addition, poor standardization in the field for phenotype characterization and assay methodology has hampered progress thus far. Duration of illness at the time of assay may have a significant impact on the level of evidence for autoimmunity, yet this characteristic is generally not mentioned in studies examining autoimmunity in OCD/tics. For example, studies in diabetes have shown levels of markers for autoimmunity to depend upon both time of onset and duration of illness (
Hathout, et al., 2000;
Mayer, et al., 2007).
The influence of prenatal exposure to maternal immune activation upon CNS development and behavior has yet to be fully explored. Prenatal exposure to cytokine levels is dependent upon plethora factors including: estrogen levels, autoimmune disease type (Th1 vs. Th2 predominant), disease activity, concurrent medications, and many other factors. Some autoimmune diseases such as rheumatoid arthritis and autoimmune thyroid diseases tend to improve during pregnancy. However, evidence exists suggesting that in subsets of immune disease-represented by lupus, certain viral and other infections-the fetus is subjected to sequelae of maternal immune dysregulation (
Atladottir, et al., 2009;
Doria, et al., 2006). These factors such as elevated cytokines and autoantibodies, in concert with genetic predisposition, may act to increase fetal cytokine signaling and expression, disrupt trophic factor and apoptotic signaling, as well as modulate cytoarchitecture in the CNS (
Golan, Lev, Hallak, Sorokin, & Huleihel, 2005). For example, animal models of prenatal administration of various cytokines have shown that increased levels of specifically IL-6 in the maternal serum play an important role in influencing the behavior of offspring (
Croonenberghs, Bosmans, Deboutte, Kenis, & Maes, 2002) (
Smith, Li, Garbett, Mirnics, & Patterson, 2007).
In this study, we examined the rates of reported autoimmune illness in the mothers of children with OCD/tics. We hypothesized that rates would be higher in these mothers than among those of the general population, and that those children determined to have the PANDAS phenotype would have mothers with the highest rates of autoimmunity.