Atypical Presentation for Friedreich Ataxia in a Child.

The classic phenotype of Friedreich ataxia is characterized by dysarthria, progressive limb and trunk ataxia, loss of reflexes, and gait disturbance with the onset of disease before the second decade. Homozygous trinucleotide repeat expansion of GAA in the FXN gene is found in 98% of patients. Two-5% of all patients have a repeat expansion on one allele and a point mutation on the other allele. Atypical phenotype is found in 25% of patients. A 10-year-old boy presented with congenital biliary atresia and progressive gait abnormality. His examination was significant for spastic gait, hyperreflexia, and sensory neuropathy. Genetic testing revealed a compound heterozygous mutation in the FXN gene. The absence of dysarthria and ataxia, retention of reflexes, absence of diabetes, and variable development of cardiomyopathy support a slow progression of disease with compound heterozygous mutation at G130V. Missense mutations are rare causes of Friedreich ataxia that can only be detected by sequencing of the FXN gene. Sequencing of the FXN gene is essential to make an early diagnosis when there is an atypical phenotype.