Trinucleotide (GAA)n repeat expansion in two families with Friedreich’s ataxia with retained reflexes

• Published in: Journal of neurology, neurosurgery and psychiatry Vol. 63; no. 6; pp. 780 - 783
• Main Authors: Kellett, Mark W, Fletcher, Nicholas A, Wood, Nicholas, Enevoldson, T Peter
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.12.1997; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: Adolescent; Adult; Age; Alleles; Ataxia; Biological and medical sciences; Cardiomyopathy; Chromosome Aberrations; Chromosome Disorders; Chromosomes, Human, Pair 9 - genetics; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Expansion; Eye movements; Female; Friedreich Ataxia - genetics; Friedreich’s ataxia; Genes - genetics; Genotype & phenotype; Humans; Medical sciences; Mutation; Neurology; Patients; Phenotype; Point Mutation - genetics; retained reflexes; Short Report; trinucleotide repeat; Trinucleotide Repeats - genetics; Wheelchairs; Human; Nervous system diseases; Linkage; Hyperreactivity; Family study; Exploration; Abnormal reflex; Cerebral disorder; Genetic disease; Central nervous system disease; Genetics; Degenerative disease; Friedreich ataxia; Tendinous areflexia; Neurological disorder; Spinal cord disease
• ISSN: 0022-3050; 1468-330X
• DOI: 10.1136/jnnp.63.6.780

In occasional families in whom cases of classic Friedreich’s ataxia (FRDA) coexist with affected cases with retained reflexes, linkage analysis has shown that both map to the FRDA locus on chromosome 9q13-21.1. A gene X25 has been identified within the critical region of the FRDA locus, and an intronic expanded GAA trinucleotide repeat has been found in most cases of FRDA. We report two further FRDA families in whom some patients with classic FRDA were areflexic whereas others had brisk reflexes. Molecular genetic analysis disclosed an abnormal trinucleotide repeat expansion within intron 1 of the FRDA gene in both phenotypes.