Different phenotypes in identical twins with cerebrotendinous xanthomatosis: case series
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Cerebrotendinous xanthomatosis (CTX) is a rare, genetically determined error of metabolism. The characteristic clinical symptoms are diarrhea, juvenile cataracts, tendon xanthomas and neuropsychiatric alterations. The aim of this study is to present a pair of identical adult twins with considerable differences in the severity of phenotype. With regards to neuropsychiatric symptoms, the predominant features were severe Parkinsonism and moderate cognitive dysfunctions in the more-affected individual, whereas these alterations in the less-affected patient were only very mild and mild, respectively. The characteristic increase in the concentrations of serum cholestanol and the lesion volumes in dentate nuclei in the brain assessed with magnetic resonance imaging were quite similar in both cases. The lifestyle conditions, including eating habits of the twin pair, were quite similar as well; therefore, currently unknown genetic modifiers or certain epigenetic factors may be responsible for the differences in severity of phenotype. This case series serves as the first description of an identical twin pair with CTX presenting heterogeneous clinical features.
KeywordsCerebrotendinous Xanthomatosis Parkinsonism Cognitive dysfunction Identical twins Heterogeneous phenotype
This study was funded by Hungarian Brain Research Program—Grant No. KTIA_NAP_13-A_II/18. Dénes Zádori was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. The linguistic corrections were made by a native English reader, Jennifer Tusz from Canada.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Written informed consent was obtained from the patients for video recording and the publication of this study (institutional research committee registration numbers are 150/2014. and 44/2016., respectively). All procedures applied during the assessment of patients were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Supplementary video 1. The Parkinsonian features of the more affected member of the identical twin pair in OFF state (AVI 22002 kb)
Supplementary video 2. The Parkinsonian features of the more affected member of the identical twin pair in ON state following levodopa challenge (AVI 19666 kb)
Supplementary video 3. The very slight Parkinsonian features of the less affected member of the identical twin pair (AVI 19687 kb)
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