Frontotemporal dementia and parkinsonism linked to chromosome 17
Autosomal dominant tauopathy with behavioral, cognitive, and motor decline.
Frontotemporal dementia and parkinsonism linked to chromosome 17, or FTDP-17, is a rare inherited neurodegenerative disorder that affects both behavior and movement. It follows an autosomal dominant pattern of inheritance and belongs to a group of conditions known as tauopathies, as well as Parkinson-plus syndromes. The condition arises from mutations in the MAPT gene, located on the long arm of chromosome 17, and is defined by three core features: shifts in behavior and personality, declining cognitive abilities, and motor problems. The disorder was formally identified at an international consensus meeting held in Ann Arbor, Michigan, in 1996.
Symptoms typically emerge slowly. Once the disease is fully developed, individuals display at least two of the three main features. However, the specific symptoms can vary widely from person to person, even among those with the same genetic mutation or within the same family. Behavioral and personality changes may include disinhibition, apathy, poor judgment, compulsive actions, heightened religiosity, substance abuse, and aggressive or abusive behavior. Early on, memory, orientation, and visual-spatial skills often remain intact despite cognitive trouble. Initial cognitive issues usually involve non-fluent speech difficulties and problems with executive function. Over time, memory and spatial skills decline, while repetitive speech patterns like echolalia and palilalia appear, eventually leading to mutism and progressive dementia.
Motor symptoms can sometimes be the first sign, and some patients are initially misdiagnosed with Parkinson’s disease or sporadic progressive supranuclear palsy. In other families, parkinsonism develops later or not at all. The parkinsonism seen in FTDP-17 is marked by symmetrical slowness of movement (bradykinesia), trouble with balance, stiffness in both the trunk and limbs, and a lack of resting tremor. It typically does not respond well to levodopa. Other movement issues can include medication-unrelated dystonia, difficulty moving the eyes upward or downward (supranuclear gaze palsy), signs of both upper and lower motor neuron damage, myoclonus, tremors during action or posture, trouble opening or closing the eyelids, swallowing difficulties, and slurred speech.
About half of FTDP-17 cases are linked to mutations in the MAPT gene, with more than 50 different disease-causing mutations
- field
- Neurodegenerative disease
- known_for
- Autosomal dominant tauopathy linked to MAPT mutations on chromosome 17
- inheritance
- Autosomal dominant
- cardinal_features
- Behavioral and personality changes, cognitive impairment, motor symptoms
- prevalence
- Very rare; over 100 families worldwide identified
Quick Facts
- Symptoms
- Loss of inhibition, inappropriate emotional responses, restlessness, neglect of personal hygiene, dementia, hallucinations, delusions, Parkinson's-like features, semantic paraphasias, and echolalia.
- Onset
- Forties or fifties.
- Causes
- Mutations in the MAPT gene.
- Diagnosis
- Clinical criteria, molecular genetic analysis, and brain imaging.
- Differential
- Pick's disease, sporadic progressive supranuclear palsy, corticobasal degeneration, Parkinson-plus syndromes, dementia with Lewy bodies, Parkinson's disease, and multiple system atrophy.
- Treatment
- Palliative and symptomatic interventions.
- Frequency
- Estimated to affect 1 in 1 million people in the Netherlands.
Facts from the source article.
Lore & Background
FTDP-17 usually appears gradually, with individuals exhibiting at least two of three cardinal features: behavioral and personality disturbances, cognitive deficits, and motor dysfunction. Clinical features differ significantly among affected individuals, even within the same family. Behavioral abnormalities may include disinhibition, apathy, poor judgment, compulsive behavior, hyperreligiosity, alcoholism, illicit drug addiction, and aggression. Memory, orientation, and visuospatial function are relatively preserved early, but progressive speech difficulties, executive dysfunction, and eventually mutism and dementia develop.
Reader's Guide
FTDP-17 is significant as a model for understanding tauopathies, linking MAPT mutations to neurodegenerative processes. Its variable presentation—even within families—highlights the complexity of genotype-phenotype correlations. The disorder is frequently misdiagnosed as Pick's disease, progressive supranuclear palsy, or corticobasal degeneration without genetic testing. Diagnosis requires clinical, pathological, and molecular genetic analysis. Treatment remains symptomatic and supportive, with prognosis ranging from months to two decades. FTDP-17 underscores the importance of genetic counseling due to incomplete penetrance and autosomal dominant inheritance.
Did You Know?
- FTDP-17 is caused by mutations in the MAPT gene on the q arm of chromosome 17.
- More than 50 pathogenic MAPT mutations have been identified, accounting for up to 50% of cases.
- Parkinsonism in FTDP-17 is distinguished by symmetrical bradykinesia, postural instability, rigidity, lack of resting tremor, and poor response to levodopa.
- The disorder was defined during the International Consensus Conference in Ann Arbor, Michigan, in 1996.
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