Schizophrenia Phenotype Preceding Behavioral Variant Frontotemporal Dementia Related to C9orf72 Repeat Expansion
Bibliographic record
Abstract
Behavioral variant frontotemporal dementia (bvFTD) shares a constellation of clinical features with primary psychiatric disorders. The discovery of new FTD-related genetic mutations has brought attention to this overlap between bvFTD and psychotic disorders. The case reported here raises the question of whether C9orf72 repeat expansion may be involved in neuropsychiatric syndromes beyond the spectrum of neurodegenerative disease. A 61-year-old woman was referred to our memory clinic for behavioral changes and progressive cognitive decline over the last 3 years. Her medical history was significant for schizophrenia since age 36, with an exacerbation of psychotic symptoms at age 55, at which time she slowly worsened, became disorganized and apathetic, and presented new perseverative behaviors. Brain MRI showed mild bilateral frontal and temporal cortical atrophy, and F-fluorodeoxyglucose PET showed bilateral frontal and anterior temporal hypometabolism. Genetic analysis revealed C9orf72 hexanucleotide repeat expansion with more than 80 G4C2 repeats. Recently, FTD due to C9orf72 repeat expansion has been reported to show a high frequency of psychotic presentations. C9orf72 repeat expansion has previously been identified as a rare but possible cause of schizophrenia spectrum disorders. Our case report is characterized by a C9orf72-associated schizophrenia phenotype preceding bvFTD by 2 decades, which might reflect early prodromal neurodegeneration or neurodevelopmental and neurobiological effects of C9orf72 repeat expansion. Analysis of C9orf72 hexanucleotide repeat expansion may be appropriate in patients with schizophrenia spectrum disorders showing new behavioral and/or cognitive changes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".