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.