Objective: To describe a case of Friedreich’s ataxia with >1700 GAA repeats but no systemic manifestations despite long disease course.

Background: Fredrich’s ataxia (FA) is due to an unstable expansion of GAA repeats in the frataxin gene on chromosome 9. The expansion size can inversely correlate with age of onset and positively correlate with the incidence of cardiomyopathy and severity of neurologic disability. Maximal repeat length till date reported in the literature is 1200. Brain MRI may be normal initially but later demonstrate cerebellar vermian and dorsal medullary atrophy. Cervical spine MRI demonstrates thinning and intramedullary signal changes. Electrophysiology is consistent with severe axonal neuropathy.

Methods: Case Report.

Results: A 59 year-old woman began having gait imbalance at age 5 years and was wheelchair bound by age 29. Due to financial reasons, she did not receive continuous neurological care. Genetic testing at age 57 revealed a >1700 GAA repeat expansion. There is no significant family history. Her current exam is significant for: kyphosis, scoliosis, pes cavus, sustained end-gaze nystagmus, ocular ataxia, dysarthria, 1/5 bilateral lower extremity power, severe axial and appendicular ataxia, severely reduced vibratory sensation and proprioception in all limbs, areflexia, and upgoing plantar response. She had superior vermian and superior cerebellar hemispheric atrophy but normal spine MRI. She had no systemic symptoms and a comprehensive workup showed normal cardiac MRI, ophthalmological evaluation, and endocrine screening. Subjectively, riluzole 50mg daily improved her hand coordination during prayer.

Conclusions: This case expands the phenotypic variability in FA. Although the large repeat expansion correlates with her significant neurological abnormalities, there were no systemic manifestations. While other genetic or environmental factors may influence her lack of systemic disease, continued observation for cardiac and endocrine abnormalities is required. The preliminary finding of mild improvement with riluzole is hopeful, as there are no treatments for FA.

References: Parkinson M et al. Clinical features of Freidreich’s ataxia: classical and atypical phenotypes. Journal of Neurochemistry. 2013;126; 103-107.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/case-of-friedreichs-ataxia-with-extremely-large-repeat-expansion-without-systemic-disease/