Frontotemporal lobar degeneration is characterized by a clinical presentation of frontotemporal dementia (FTD) with evidence of an FTD-causing mutation (eg, C9ORF72) or histopathologic FTD. FTD is a type of dementia associated with atrophy of the frontal and temporal lobes. Behavioral-variant FTD (Pick disease), semantic-variant primary progressive aphasia, and nonfluent variant primary progressive aphasia are considered different clinical forms of FTD. This variation in presentation is due to the focal area of degeneration, which can progress and spread over time.

These disorders are characterized by behavioral changes and/or language disturbance. Behavior can be impulsive or apathetic, and affected patients may exhibit inappropriate social behavior and disinhibition, lack of empathy, changes in food preference, hypersexuality, compulsive or perseverative behaviors, agitation, blunted emotions, neglect of personal hygiene, distractibility, or lack of motivation. Language disturbance can include difficulty with speech production or comprehension. Memory and visual spatial skills are typically intact. Eventually, there can be global cognitive impairment and motor decline, such as parkinsonism or motor neuron disease.

FTD can also overlap with cortical basal degeneration, progressive supranuclear palsy, frontal variant Alzheimer disease, and motor neuron disease. Age of onset is usually 50-65 years. Prognosis is poor with rapid, steady deterioration and death within 8-15 years of symptom onset, typically due to secondary infections, such as pneumonia. FTD affects men and women equally.

Patients with this disorder may have an increased risk of various general medical conditions.