Screening for the LRRK2 G2019S and codon-1441 mutations in a pathological series of parkinsonian syndromes and frontotemporal lobar degeneration.

BACKGROUND

The neuropathology associated with LRRK2 mutations is heterogeneous but Lewy body (LB) type pathology is the most common substrate encountered. While the prevalence of LRRK2 mutations has been extensively studied in Parkinson's disease (PD), limited information is available on the frequency of LRRK2 mutations in dementia with Lewy bodies (DLB) and in other pathological conditions associated with these mutations, such as non-specific nigral degeneration without LB, tau-immunopositive neurofibrillary tangle pathology, and ubiquitin-positive neuronal inclusions resembling those observed in a subtype of frontotemporal lobar degeneration (FTLD-U).

OBJECTIVE

To further investigate the neuropathology associated with LRRK2 mutations.

METHODS

We have screened for the LRRK2 G2019S and codon-1441 (R1441G/C/H) mutations in 110 cases from a Spanish Brain Bank, which include: 66 synucleinopathies (33 PD, 25 DLB and 8 multiple system atrophy cases), 29 tauopathies (21 progressive supranuclear palsy, 3 corticobasal degeneration and 5 tau-positive FTLD cases), 3 cases of non-specific nigral degeneration and 12 tau-negative FTLD (9 FTLD-U and 3 dementia lacking distinctive histology cases).

RESULTS

The G2019S mutation was found in two cases: One case had a clinical and pathological diagnosis of PD and the other suffered from typical PD and on neuropathological examination had non-specific nigral degeneration without LB. A synonymous variant (R1441R; c.4323C>T) was detected in another PD case.

CONCLUSIONS

In this brain bank-based series, LRRK2 G2019S mutation occurred in patients with parkinsonism associated with either typical brainstem LB pathology or non-specific nigral degeneration. LRRK2 mutations were not encountered in other neurodegenerative disorders associated with synuclein and tau deposition.