Frontotemporal dementia is the second most common cause of dementia in patients under 65. It typically presents in the 50s-60s — often misdiagnosed as depression, midlife crisis, marital problems, or substance use for years before the neurodegenerative diagnosis is made.
Three major variants:
Behavioral variant (bvFTD) — most common. Personality and behavioral change: disinhibition (socially inappropriate behavior, loss of social judgment), apathy (loss of motivation, social withdrawal), loss of empathy (callousness, decreased interest in others), perseverative or compulsive behaviors (repetitive activities, food preferences shifting toward sweets, hoarding), hyperorality (overeating, dietary changes), cognitive changes (executive dysfunction with relatively preserved memory).
Semantic variant primary progressive aphasia (svPPA) — loss of word meaning. Patients can speak fluently but progressively lose the meaning of words. "What is a watch?" The patient sees the watch but cannot retrieve its name or function.
Nonfluent/agrammatic variant PPA (nfvPPA) — effortful, agrammatic speech with relatively preserved comprehension. Patient produces fewer words, simpler structures, with apparent struggle.
Pathology: heterogeneous — different molecular pathologies (TDP-43, tau, FUS) underlie different clinical presentations. Genetic forms (MAPT, GRN, C9orf72 mutations) account for ~30% of cases. Strong family history substantially raises suspicion.
Diagnostic features distinguishing FTD from AD:
Age: often 50-65 (vs typical AD age 65+).
First symptoms: personality/behavioral or language (vs memory in AD).
Memory: often relatively preserved early in FTD (vs prominent loss in AD).
Imaging: frontotemporal atrophy on MRI (vs hippocampal/parietotemporal in AD). FDG-PET shows frontal/temporal hypometabolism.
Cholinesterase inhibitor response: can worsen FTD symptoms (vs modest benefit in AD).
FTD is one of the most commonly missed diagnoses in psychiatry. A middle-aged patient with new disinhibition, dietary changes, and apathy presents to a primary care physician. Depression is diagnosed. SSRI is started. The patient does not respond. The behavior worsens. Years pass. Eventually neuroimaging is obtained and shows frontotemporal atrophy. By then, substantial cognitive and behavioral decline has occurred.
Treatment: no disease-modifying treatment. SSRIs for disinhibition, agitation, behavioral symptoms — best evidence among pharmacologic options. Avoid cholinesterase inhibitors — can worsen agitation. Antipsychotics with extreme caution (FTD patients can show neuroleptic sensitivity). Speech therapy for PPA variants. Family education and safety planning critical given personality changes and impaired judgment. Power of attorney and advance care planning before further decline.
When you encounter a middle-aged patient with new personality changes that family describes as "not himself" or "not herself," FTD belongs in the differential. Earlier recognition allows planning, family support, and treatment of treatable symptoms. The diagnosis is consequential.