Idiopathic environmental intolerance: Increased prevalence of panic disorder-associated cholecystokinin B receptor allele 7

Background: A growing body of evidence suggests that idiopathic environment al intolerance (IEI) is a psychophysiologic disorder with prominent feature s of anxiety/panic and somatization, although proponents of a toxicogenic e xplanation claim, despite a lack of convincing evidence, that symptoms aris e from exposure to otherwise nonnoxious environmental agents. Patient behav iour is characterized by strenuous avoidance of perceived triggers to the p oint of severe impairment of normal social and vocational functioning. IEI proponents claim that previous studies showing a high prevalence of psychop athology in patients with IEI and studies showing panic responses to known panicogenic challenges merely reflect the anxiety-producing result of livin g with IEI, Objective: We explored whether IEI and panic disorder, personality traits, or both shared an underlying neurogenetic basis that would predate the anxi ety of IEI symptomatology. The DNA of patients with IEI was examined for th e presence of known panic disorder-associated cholecystokinin B (CCK-B) rec eptor alleles and for personality trait-associated dopamine D4 receptor pol ymorphisms. Methods: Eleven patients with typical IEI symptoms were recruited and were individually matched to normal control subjects from an existing bank for a ge, sex, and ethnic background. Genomic DNA was extracted from peripheral b lood samples. CCK-B and dopamine D4 receptor polymorphisms were examined by using standard PCR-based techniques, Results: There was a significantly higher prevalence of the panic disorder- associated CCK-B receptor allele 7 in subjects with IEI (9/22 [40.9%) compa red with control subjects (2/22 [9,1%, P = ,037), There was no difference i n personality trait-associated polymorphisms of the gene encoding dopamine D4 receptor between patients and control subjects. Conclusions: These findings provide preliminary evidence that IEI and panic disorder share a common neurogenetic basis, which would predate the anxiet y-producing effects of IEI symptoms, Further studies with larger samples ar e warranted, but these results support previous studies that suggest that p anic disorder may account for much of the symptomatology in at Least some c ases of IEI and provide a basis for rational treatment strategies.