Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay due to Novel Mutations in the SACS Gene

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is characterized by triad of progressive cerebellar ataxia, progressive spasticity, and axonal/demyelinating peripheral neuropathy. Other manifestations include dysarthria, weakness in lower extremities and distal muscle wasting, foot deformities, retinal striation, prolapse of the mitral valve and rarely intellectual disability, hearing loss, and myoclonic epilepsy. We describe a patient who developed peripheral sensorimotor neuropathy in the absence of spasticity on initial presentation. He had nerve root enhancement on magnetic resonance imaging (MRI) lumbar spine, and nerve conduction studies were suggestive of demyelinating polyneuropathy. Patient had mild cerebellar atrophy on MRI and some delay of motor milestones. Over the course of several months, he developed spasticity, and genetic analysis together with clinical presentation was consistent with ARSACS. He was noted to have a pathogenic mutation c.8108G>A (p. Arg2703His) inherited from mother and a variant of uncertain significance c.7216T>C (p. Ser2406Pro) inherited from his father in SACS gene. Atypical cases may present later in life or in absence of one of the classical features at the time of presentation, which may make diagnosis difficult. Our patient had such an atypical presentation of ARSACS. Young patients with neuropathy and concomitant cerebellar atrophy on MRI should raise suspicion for hereditary spastic ataxia syndrome. Follow-up examination can often reveal additional findings to aid the diagnosis.