Which diagnosis is characterized by gait ataxia, dysarthria, scoliosis, and is caused by GAA repeat expansion in the frataxin gene?

• A. Ataxia telangiectasia
• B. Friedreich ataxia
• C. Spinocerebellar ataxia
• D. Vitamin E deficiency

Answer: (B)

Friedreich ataxia is characterized by a combination of gait ataxia, dysarthria, and scoliosis, and it stems from a GAA repeat expansion in the frataxin (FXN) gene. This autosomal recessive disorder causes reduced frataxin protein, which is essential for mitochondrial iron-sulfur cluster assembly. Without enough frataxin, mitochondria malfunction and oxidative stress increases, leading to degeneration of the dorsal columns, spinocerebellar tracts, and peripheral nerves. The clinical picture reflects this with progressive gait instability and slurred speech, and scoliosis is a common accompanying feature in affected individuals. Additional clues often seen include pes cavus, diabetes, and hypertrophic cardiomyopathy. The specific genetic mechanism—GAA repeat expansion in FXN—distinguishes Friedreich ataxia from other ataxias and vitamin deficiencies.