Background
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron degeneration with phenotypic heterogeneity, including age at onset. Juvenile ALS (JALS) includes ALS patients aged less than 25 years who typically show slow progression. This study aimed to identify the characteristics of juvenile ALS from Korean ALS cohorts.
Methods
We retrospectively investigated the clinical characteristics of JALS patients, who met the revised El Escorial-Airlie House criteria, in the Korean motor neuron disease cohort om January 2002 to November 2018. To evaluate the genetic background ofin JALS, we screened the SOD1 mutation in all JALS patients using PCR.
Results
Among the seven JALS patients, the mean age was 22.1 years (± 2.19 years) and 4 patients were male. Most patients were diagnosed within less than 12 months, but in one patient, it took 96 months to make the initial diagnosis. On assessing the cognitive function, none of the patients had dementia. The progression rate of JALS during follow-up was usually low (median [IQR], 0.31 [0.11-0.52]), except in patients with SOD1 mutation (3.40) and CLEC4C mutation (1.12). One patient revealed a family history of ALS with SOD1 mutation, but we also detected the SOD1 mutation among sporadic JALS patients.
Conclusions
Although JALS patients with genetic mutations (SOD1-p.Asn87Ser and CLEC4C-p.Lys210*) showed faster progression than other JALS patients, one patient with SOD1 mutation (p.Gly17Ala) showed slow progression. Familial ALS was rare; however, it might be caused by low or incomplete penetrance of the genes or by small number of JALS patients. To investigate the other genetic causes of JALS without the SOD1 mutation, a further study including detailed genetic analysis is needed.

We report a 23-year-old woman with adult Sandhoff disease, who presented with motor neuron disease phenotype. The patient had experienced progressive motor weakness in four extremities since 1 year prior to admission. Electrophysiological study revealed wide-spread denervation potentials, and the assay of total hexosaminidase involving A and B activities showed decreased levels of these activities, which was consistent with Sandoff disease. This is the first Korean case of adult Sanhoff disease presented as a motor neuron disease phenotype.