The portal for rare diseases and orphan drugs

Spinocerebellar ataxia type 36 (SCA36) prevalence is unknown. SCA36 has been described in more than 100 families in Asia (Japan and China) and Europe (France, Italy, Poland, and Spain-Galicia). In a US population, SCA36 accounts for 0.7% of disease in a large undiagnosed ataxia cohort.

SCA36 presents in adulthood with ataxic dysarthria, truncal ataxia, limb ataxia, general hyperreflexia and variably occurring lower limb spasticity. Motor neuron involvement occurs later in the disease course and manifests with fasciculations and atrophy of the skeletal muscles and tongue. Sensorineural hearing loss may also be present in some. Oromandibular dystonia is a rare manifestation. Only mild cerebellar atrophy is reported.

SCA36 is due to a pathogenic heterozygous GGCCTG repeat expansion in intron 1 of the NOP56 gene (20p13).

Diagnosis is based on the characteristic clinical findings and molecular genetic testing. As the manifestations of SCA36 are not specific, diagnosis is only confirmed with the finding of a pathogenic heterozygous GGCCTG repeat expansion in intron 1 of the NOP56 gene.

Differential diagnosis includes other types of ADCA (Autosomal dominant cerebellar ataxia).

Antenatal diagnosis is possible in families with a known genetic cause.

SCA36 is inherited autosomal dominantly and genetic counseling is possible. Genetic counseling should be proposed to individuals having the disease-causing mutation informing them that there is 50% risk of passing the mutation to offspring.

There is no cure for SCA36 and treatment is supportive. Physical therapy, as well as the use of canes and walkers, should be offered in order to maximize strength and maintain activity. Wheelchairs are eventually necessary. Speech therapy and communication devices may be useful to those with dysarthria. Annual neurological examinations are recommended to monitor disease progression.