Blood harmane (1-methyl-9H-pyrido[3,4-b]indole) concentration in dystonia cases vs. controls

•Harmane (1-methyl-9H-pyrido[3,4-b]indole) is a potent neurotoxin.•Harmane has been linked with several tremor disorders.•Blood harmane levels were quantified by high performance liquid chromatography.•Blood harmane levels were similar in dystonia cases vs. controls.•Elevated blood harmane is not a broad feature of all neurological diseases.

BackgroundHarmane (1-methyl-9H-pyrido[3,4-b]indole) (HA) is a potent neurotoxin that has been linked to two neurological diseases, essential tremor and Parkinson's disease. Blood harmane concentrations [HA] are elevated in patients with both diseases. An important question is whether HA is specifically linked with these diseases or alternatively, is a non-specific marker of neurological illness.ObjectivesWe assessed whether blood [HA] was elevated in patients with a third neurological disease, dystonia, comparing them to controls.MethodsBlood [HA] was quantified by high performance liquid chromatography. Subjects comprised 104 dystonia cases and 107 controls.ResultsMean log blood [HA] in dystonia cases was similar to that of controls (0.41 ± 0.51 g−10/ml vs. 0.38 ± 0.61 g−10/ml, t = 0.42, p = 0.68). In unadjusted and adjusted logistic regression analyses, log blood [HA] was not associated with the outcome (diagnosis of dystonia vs. control): odds ratio (OR)unadjusted = 1.11, 95% confidence interval (CI) = 0.69–1.79, p = 0.68; ORadjusted = 1.07, 95% CI = 0.58–1.97, p = 0.84.ConclusionsIn contrast to the elevated blood [HA] that has been reported in patients with essential tremor and Parkinson's disease, our data demonstrate that blood [HA] was similar in patients with dystonia and controls. These findings provide the first support for the notion that an elevated blood [HA] is not a broad feature of neurological disease, and may be a specific feature of certain tremor disorders.