Alzheimer's disease (AD) is strictly connected with aging and frailty. Although dementia contributes to frailty, it is not well established whether AD patients could be per se defined "frail". At the same time, it is not known whether among AD patients, which are a heterogeneous group of patients, it is possible to identify a subgroup of frail individuals. In this work we sought indices useful to identify "the frail AD". To do this we evaluated disease progression rate and response to pharmacological treatment (Mini Mental State Examination evaluation), cerebrospinal fluid biomarkers (amyloid-β.42, total-tau and phospho-tau) levels, inflammatory indices (serum c-reactive protein, fibrinogen, D-Dimers) in a group of patients with a diagnosis of probable AD. Our results describe the clinical profile of patients which could be considered as non-responders and rapidly progressive AD. In the absence of other indices we conclude that patients with these features could well be considered "frail" among AD.