Clinical-pathological studies remain the gold-standard for the diagnosis of Parkinson’s disease (PD). However mounting data from genetic-PD autopsies challenge the diagnosis of PD based on Lewy body pathology. Most of the confirmed genetic risks for PD show heterogenous neuropathology, even within kindreds, which may or may not include Lewy body pathology.
Here we review the literature of genetic-PD autopsies from cases with molecularly-confirmed PD or parkinsonism and summarize main findings on SNCA (n=25), Parkin (n=20, 17 bi-allelic and 3 heterozygotes), PINK1 (n=5, 1 bi-allelic and 4 heterozygotes), DJ-1 (n=1), LRRK2 (n=55), GBA (n=10 Gaucher disease patients with parkinsonism), DNAJC13, GCH1, ATP13A2, PLA2G6 (n= 8 patients, two with PD), MPAN (n=2), FBXO7, RAB39B and ATXN2 (SCA2), as well as on 22q deletion syndrome (n=3). Findings from autopsies of heterozygous mutation carriers of genes which are traditionally considered recessively-inherited are also discussed.
Lewy bodies may be present in syndromes clinically distinctive from PD (e.g., MPAN-related neurodegeneration) and absent in patients with clinical PD syndrome (e.g., LRRK2-PD or Parkin-PD). Therefore, we may conclude that the presence of Lewy bodies are not specific to the diagnosis of PD and that PD can be diagnosed even in the absence of Lewy body pathology.
Interventions that reduce alpha-synuclein load may be more justified in SNCA-PD or GBA-PD than in other genetic forms of PD. The number of reported genetic-PD autopsies remains small and there are limited genotype-clinical-pathological-phenotype studies. Therefore, larger series of autopsies from genetic-PD patients are required.