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.

KEYWORDS : Amyotrophic lateral sclerosis, Motor neuron disease