Supplementary Material for: Clinical Characteristics of C9ORF72-Linked Frontotemporal Lobar Degeneration

<b><i>Background:</i></b> The most common genetic cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) has been linked to a hexanucleotide repeat expansion in the <i>C9ORF72</i> gene. The frequency of the <i>C9ORF72</i> expansion in Finland is among the highest in the world. <b><i>Methods:</i></b> We assessed 73 Finnish patients with FTLD in order to examine the clinical characteristics associated with the expanded <i>C9ORF72</i>. Demographic and clinical features were evaluated. As a potential disease modifier, the apolipoprotein E <i>(APOE)</i> genotype was also assessed. Neuropathological analysis was available on 2 expansion carriers and 1 non-carrier. <b><i>Results:</i></b> The <i>C9ORF72</i> expansion was present in 20 of 70 (29%) probands. Significant associations with the <i>C9ORF72</i> expansion were observed for concomitant ALS and positive family history of dementia or ALS. Psychoses were detected in both carriers and non-carriers (21 vs. 10%, p = 0.25). The <i>APOE</i> ε4 allele did not cluster among expansion carriers. Numerous p62-positive neuronal inclusions were detected in the cerebellar cortex of the 2 expansion carriers. <b><i>Conclusion:</i></b> In line with the suggested <i>C9ORF72</i> core phenotype, we also detected a high frequency of neuropsychiatric symptoms; however, these symptoms seem not be specific to <i>C9ORF72</i>-associated FTLD. FTLD should be considered in cases of middle-age-onset psychosis.