Volume 6 ; Issue 1 ; in Month : Jan-June (2025) Article No : 113
Sanjiv Chamraj* and Sharan Srinivasan

Abstract

Autosomal dominant spinocerebellar ataxia type 48 (SCA48) is a newly identified subtype of SCA, marked by early onset of ataxia and cognitive impairment, and is associated with mutations in the STIP1 homology and U-box-containing protein 1 (STUB1) gene. We reported a case of novel de novo STUB1 variant cause of SCA48 presented with subacute ataxia with broad-based gait, mild incoordination of limbs, and mild dysarthria in 50-year-old female patient. Patient has no familial history of similar illness or other neurologic disorders. She did not have other abnormal movements such as parkinsonism, dystonia, chorea, or myoclonus. She had normal cognitive function. Patient’s Scale for the Assessment and Rating of Ataxia (SARA) score was 7. Tendon reflexes were normal. Serum autoimmune encephalitis and paraneoplastic neuronal antibodies tests were negative. Sensory and plantar flexors were normal. Serum autoimmune encephalitis and paraneoplastic neuronal antibodies work-ups were negative. Brain magnetic resonance imaging (MRI) indicated mild cerebellar atrophy, small vessel ischemic changes, and calcified granuloma in left frontal region with no surrounding perilesional oedema. A nerve conduction study indicated no evidence of peripheral neuropathy or other abnormalities. The whole exome sequencing test identified the heterozygous missense variant “c.206G>C; p.Cys69Ser,” detected in the STUB1 gene on chromosomal position chr16:681198:G>C. This variant is noted to have a total depth of 74X. It is located in exon 2 of the transcript NM_005861.4 and it leads to a change in amino acid from Cysteine to Serine at codon 69. The detected STUB1 gene “c.206G>C; p.Cys69Ser,” variant in our case of 50-year-old female has not been previously reported among Indian population. In conclusion, we reported the unusual, uncommon case of SCA48 caused due to a novel de novo STUB1 gene variant “c.206G>C; p.Cys69Ser,” in the chromosomal position chr16:681198:G>C led to a change in amino acid from Cysteine to Serine at codon 69 in 50-year-old female patient from southern India presented with clinical conditions such as subacute ataxia with broad-based gait, mild incoordination of limbs, and mild dysarthria.

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