A Novel <i>de novo</i> Exon 21 DNMT1 Mutation Causes Cerebellar Ataxia, Deafness, and Narcolepsy in a Brazilian Patient
Bibliographic record
Abstract
STUDY OBJECTIVES: Autosomal dominant cerebellar ataxia, deafness and narcolepsy (ADCA-DN) is caused by DNMT1 mutations. Diagnosing the syndrome can be difficult, as all clinical features may not be present at onset, HLA-DQB1*06:02 is often negative, and sporadic cases occur. We report on clinical and genetic findings in a 31-year-old woman with cerebellar ataxia, deafness, and narcolepsy, and discuss diagnostic challenges. DESIGN: Clinical and genetic investigation in a patient and family members. SETTING: Ataxia clinic, São Paulo, Brazil. PATIENTS OR PARTICIPANTS: One patient and her family members. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Narcolepsy was supported by polysomnographic and multiple sleep latency testing. HLA-DQB1*06:02 was positive. CSF hypocretin-1 was 191 pg/mL (normal values > 200 pg/mL). Mild brain atrophy was observed on MRI, with cerebellar involvement. The patient, her asymptomatic mother, and 3 siblings gave blood samples for genetic analysis. DNMT1 exons 20 and 21 were sequenced. Haplotyping of polymorphic markers surrounding the mutation was performed. The proband had a novel DNMT1 mutation in exon 21, p.Cys596Arg, c.1786T > C. All 4 parental haplotypes could be characterized in asymptomatic siblings without the mutation, indicating that the mutation is de novo in the patient. CONCLUSIONS: The Brazilian patient reported here further adds to the worldwide distribution of ADCA-DN. The mutation is novel, and illustrates a sporadic case with de novo mutation. We believe that many more cases with this syndrome are likely to be diagnosed in the near future, mandating knowledge of this condition and consideration of the diagnosis.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".