Familial segmental spinal myoclonus: a rare clinical feature of Friedreich's ataxia.

Introduction: Friedreich's ataxia (FRDA) is the most common autosomal recessive inherited ataxia. It is characterized by onset before the age of 25 year, progressive limb and truncal ataxia, lower limb areflexia, extensor plantars, dysarthria and impaired posterior column sensations. Other important associated features are skeletal deformity, hypertrophic cardiomyopathy and diabetes mellitus. Most of the patients (98%) have an unstable homozygous trinucleotide (GAA) expansion in intron-1 of chromosome 9 and 2% patients are compound heterozygous for GAA expansion and point mutations.

Case Description: We observed an adolescence onset FRDA exhibiting spinal segmental myoclonus (SSM) in a family. Triplet repeat primed polymerase chain reaction (TP-PCR) demonstrated unstable expansion of >66 GAA repeats.

Conclusions: SSM is a unique and rare manifestation of FRDA. This might be the first case report of SSM in FRDA patient.