American Board of Psychiatry and Neurology (ABPN) Practice Exam 2026 - Free ABPN Practice Questions and Study Guide

The characteristic that is not associated with Parkinson's disease is an increase in carbohydrate-deficient transferrin. This specific finding is usually linked to conditions like chronic alcohol consumption or certain liver diseases where there is altered glycosylation of transferrin, but it does not pertain to the pathological or physiological features of Parkinson's disease.

In contrast, the other characteristics listed are closely related to Parkinson's disease. The resting 4- to 6-Hz tremor is a classic motor symptom often observed in individuals with this condition, typically manifesting in the hands or fingers while at rest. Being classified as a synucleinopathy reflects the involvement of α-synuclein protein aggregates, which play a critical role in the pathology of Parkinson's disease, illustrating the neurodegenerative processes at work. Loss of pigment in the substantia nigra is also a hallmark of Parkinson's disease, as this region of the brain is affected due to the degeneration of dopaminergic neurons, leading to the characteristic motor deficits associated with the disease. Therefore, the other options highlight essential features of Parkinson's, while an increase in carbohydrate-deficient transferrin is not relevant to its pathology.