An association with frequent streptococcal infections has led to the hypothesis that some children with OCD have impaired humoral immune function (Swedo et al. 1998; Murphy et al. 2004). Indeed, a recent survey of 908 patients with PANS concluded that immune dysfunction is “pervasive,” with 53% of patients tested for some measure of immune status showing at least one abnormality, although there was no control group (Calaprice et al. 2017). In particular, 25% reported a diagnosis of immunodeficiency, most commonly hypogammaglobulinemia, although interpretation of these data is complicated by collection of samples during possible acute infection; moreover, based on typical assay protocols the actual prevalence of specific abnormalities (e.g., low immunoglobulin G) appeared comparable to expected values (Walker et al. 1994). There have also been preliminary reports of low IgA levels in patients with OCD compared with anxiety disorders or attention-deficit/hyperactivity disorder (Williams 2016).
