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A Natural History Study of Timothy Syndrome.
Katherine W Timothy1, Rosemary Bauer2,3, Kerry A Larkin2,4
1The Timothy Syndrome Foundation, Charitable Organization, Brigham City, UT, USA.
Orphanet Journal of Rare Diseases
|November 23, 2024
Summary
Timothy syndrome, caused by CACNA1C variants, presents with both cardiac and extra-cardiac symptoms in all patient groups. This includes those previously thought to have non-syndromic long QT type 8, highlighting the disease
Area of Science:
- Genetics and Molecular Biology
- Cardiology
- Neurology
- Endocrinology
Background:
- Timothy syndrome is a rare genetic disorder caused by variants in the CACNA1C gene.
- Initially defined by long QT syndrome and syndactyly linked to the Gly406Arg variant, the clinical spectrum is now known to be broader.
- The classification of 'cardiac-only' or non-syndromic Timothy syndrome requires further investigation regarding long-term cardiac selectivity.
Purpose of the Study:
- To comprehensively investigate the clinical manifestations of Timothy syndrome across different genotypic and diagnostic categories.
- To determine if overlapping cardiac and extra-cardiac symptoms exist in patients classified as non-syndromic long QT type 8.
- To provide a detailed natural history of Timothy syndrome.
Main Methods:
- A survey was administered to parents of patients diagnosed with Timothy syndrome.
- Participants were categorized into five groups based on genotype and initial diagnosis for comparative analysis.
- Data collected included a wide range of cardiac and extra-cardiac symptoms and clinical features.
Main Results:
- Timothy syndrome patients frequently exhibit both cardiac and extra-cardiac features, including long QT syndrome, neurodevelopmental impairments, hypoglycemia, and respiratory issues.
- The prevalence of these features was consistent across all patient categories, including those with a non-syndromic long QT type 8 diagnosis.
- This suggests that the 'non-syndromic' classification may not accurately reflect the full clinical picture.
Conclusions:
- This study provides the first natural history overview of Timothy syndrome, confirming the syndromic nature of CACNA1C variants.
- Both cardiac and extra-cardiac manifestations are prevalent in all patient groups, challenging the concept of cardiac-selective forms.
- Hypoglycemia and respiratory dysfunction are significant, life-threatening risks in Timothy syndrome, necessitating comprehensive management strategies.
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