Pathologically Confirmed Alzheimer's Disease Presenting as Clinical Parkinson's Disease, A Case Report

It is well known that rare cases of Alzheimer's disease (AD) pathology may cause corticobasal or posterior cortical atrophy syndromes, and that cases with advanced AD may develop parkinsonism. However, reports of parkinsonism as an initial manifestation of AD have rarely been documented.

To demonstrate that a syndrome meeting all criteria for a clinical diagnosis of idiopathic Parkinson's disease (PD) may be an initial and years-long sustained manifestation of pathologically confirmed AD.

Clinico-pathological case.

We present a case with a 12-year clinical presentation consistent with a typical course of idiopathic Parkinson's disease, including dementia developing 6 years after the PD diagnosis. The patient improved, but only mildly, to standard treatment for PD motor symptoms. The neuropathological examination identified AD changes, and no evidence to support a concomitant diagnosis of PD.

The absence of alpha-synucleinopathy, coupled with the patient's dementia history and AD changes in neuropathological examination, indicated the diagnosis of AD and no supplementary explanation. Neuronal loss with neurofibrillary tangles and amyloid plaques in the brainstem, substantia nigra, and locus coeruleus likely contributed to Parkinsonism features.