Atypical presentation of amyotrophic lateral sclerosis with <i>SOD1</i>-H47R mutation

Traditionally, amyotrophic lateral sclerosis (ALS) is recognised as a fatal neurodegenerative disease that typically emerges in the later decades of life, with a life expectancy of 2-5 years after symptom onset. We now understand that ALS exhibits a wide phenotypic clinical spectrum, significantly influenced by genetic factors. Here, we describe a patient with familial ALS carrying a heterozygous pathogenic H47R mutation of the superoxide dismutase 1 (<i>SOD1</i>) gene. His clinical presentation is atypical, with a slow progressive course, lower extremity weakness, and sparing of bulbar and respiratory function, consistent with the flail leg variant of ALS. The objective of this report is to increase awareness of atypical presentations of ALS and the diagnostic challenges they pose to clinicians. In addition to a description of the clinical case, we briefly discuss the new role of gene therapy in the treatment of familial ALS with <i>SOD1</i> mutations.