Amyotrophic lateral sclerosis (ALS) constitutes the main type of motor neuron disease. Familial ALS is characterized by the presence of positive family history and accounts for 10% of ALS cases. Although familial ALS is the main culprit for early-onset disease, there are rare cases of early- or young-onset ALS with negative family history or sporadic ALS. We describe a 23-year-old man with clinical and electrophysiological evidence of probable sporadic ALS according to the revised EI Escorial criteria. Interestingly, brain neuroimaging revealed bilaterally increased T2 signals across corona radiata, posterior limb of the internal capsule, and descending motor tracts in the brainstem and hypointensity rim of the motor cortex on T2-weighted images. Young-onset sporadic ALS may be a distinct nosological entity. The topic is shortly discussed in the light of its genetic and clinical characteristics.