Parkinson's Disease Associated with G2019S LRRK2 Mutations without Lewy Body Pathology

Background The G2019S leucine‐rich repeat kinase 2 (LRRK2) gene mutation is an important and commonly found genetic determinant of Parkinson's disease (PD). The neuropathological findings associated with this mutation have thus far been varied but are most often associated with Lewy body (LB) pathology. Objective Describe a case of clinical Parkinson's disease with levodopa responsiveness found to have LRRK2 mutations and the absence of Lewy bodies. Method We present an 89‐year‐old man with a 10‐year history of slowly progressive parkinsonism suspected to be secondary to Parkinson's disease. Results Neuropathological evaluation revealed nigral degeneration without Lewy bodies or Lewy neurites, but there were frequent tau‐immunopositive neurites and astrocytes in the putamen and substantia nigra, neocortical glial tau positive astrocytes associated with aging‐related tau astrogliopathy (ARTAG), as well as neurofibrillary tangles, beta amyloid plaques, and amyloid angiopathy typical of advanced Alzheimer's disease. G2019S LRRK2 homozygous mutations were found. Conclusion This case illustrates that levodopa‐responsive clinical PD caused by G2019S LRRK2 mutations can occur without Lewy bodies.