Huntington's disease (HD) is an autosomal progressive neurodegenerative disorder 
caused by the expansion of CAG repeats in the HTT gene. Intermediate alleles 
(IAs) are in the range of 27-35 repeats and have been associated to a normal 
phenotype. The aim of this work was to analyze the association between 
intermediate huntingtin CAG-repeat alleles (IAs) and neurodegenerative diseases, 
other than HD. We screened the HTT CAG repeats in patients with Alzheimer's 
disease (AD) (n = 1126), Parkinson's disease (PD) (n = 610), and frontotemporal 
lobar degeneration (FTLD) (n = 225). We also studied 509 healthy controls (HCs). 
The relative frequency of IAs for each group was 6.03% in AD, 5.3% in FTLD, 3.5% 
in PD, and 2.9% in HCs. The frequency of IA was significantly higher among 
patients with AD when compared to HCs (p = 0.011, OR = 2.11, 95% CI = 
1.19-3.74); no significant difference was observed in FTLD (p = 0.17; OR = 1.88, 
95% CI = 0.85-4.03) and PD (p = 0.69; OR = 1.21; 95% CI (0.61-2.37) versus HCs. 
No atypical symptoms or clinical features distinctive of HD were found among 
carriers of IAs. We found 3 cases with CAG expansions within the pathological 
range, one diagnosed with AD, one with PD, and one with FTD. Results suggest 
that IAs might have a role in the pathogenesis of AD. In addition, HD patients 
might be misdiagnosed with other neurodegenerative diseases, particularly when 
CAG repeats are in the lower pathological range.