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.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-015-1121-5) contains supplementary material, which is available to authorized users.

Molecular genetic analysis of trinucleotide repeat disorders (TRDs) in Indian population and application of repeat primed PCR

Trinucleotide repeat disorders (TRDs) are a set of genetic disorders caused by trinucleotide repeat expansion in certain genes that exceed the normal, stable threshold, which varies from gene to gene. A dynamic mutation in a healthy gene may increase the repeat count and result in a defective gene. At present there are 14 pathogenic trinucleotide repeat disorders that are known to affect humans. The occurrence of these "triplet repeat diseases" within populations ranges from fairly common (Fragile X syndrome and Myotonic dystrophy type 1) to rare (Dentatorubral-pallidoluysian atrophy). In the present study we report a detailed scenario of TRDs in India mostly in respect to the 9 most common disorders namely; Fragile X syndrome, Myotonic dystrophy type 1, Spinocerebellar ataxia (type 1, 2, 3, 6 and 7), Friedreich Ataxia and Huntington Disease.