SLC6A3 and semantic dementia: Additionally, one patient had biallelic POLG mutations leading to tremor-dominant parkinsonism in her fifth decade with altered DAT-Scan, associated with palpebral ptosis and later in life with myopathy and peripheral neuropathy; one patient carried a pathogenic GRN mutation and received a diagnosis of FTDP (frontotemporal dementia-parkinsonism) with a clinical presentation consistent with a PD phenocopy (Fig. 1B, Supplementary Table III).