Which of the following is a supportive feature of Parkinson's disease?

• A. Olfactory loss
• B. Autonomic failure
• C. REM sleep behavior disorder
• D. Early personality changes

Answer: (A)

Olfactory loss is a classic early non-motor feature that supports a Parkinson's disease diagnosis. Many patients notice a reduced sense of smell years before motor symptoms appear, reflecting early alpha-synuclein–related involvement of olfactory pathways. Because this olfactory dysfunction can help distinguish Parkinson's from other movement disorders where smell is usually preserved, it is considered a supportive criterion in diagnostic frameworks.

Autonomic failure, while common in Parkinson's, is not as specific and can occur in other conditions such as multiple system atrophy, so it’s less useful as a distinctive supportive criterion. REM sleep behavior disorder is strongly associated and often predates Parkinson's, but in some diagnostic schemes it is viewed more as a prodromal marker than a standard supportive feature. Early personality changes are not typical features used to support a Parkinson's diagnosis.