Familial ALS With p. L127S (L126S) Variant of the Cu/Zn SOD1 Gene: A Report of Two New Cases and Literature Review.

Herein, we report two autopsy cases of familial ALS with a p. L127S (L126S) SOD1 variant. Case 1 involved a 62-year-old woman who presented with lower-extremity muscle weakness with lower motor neuron signs. The patient developed bulbar palsy and died of respiratory failure 9 years after onset. Case 2 (the second son of Case 1) presented with lower-extremity muscle weakness at the age of 38 years, with upper and lower motor neuron signs and died of respiratory failure 8 years after onset. The pathological findings in both cases predominantly consisted of lower motor neuron loss and degeneration of the lateral and posterior funiculi. Numerous conglomerate hyaline inclusions (CHIs) were observed in the remaining motor neurons. Vacuole formation was observed inside the inclusions, sometimes with granular structures. Some inclusions were positive for ubiquitin, p62, and SOD1. Electron microscopy revealed that CHIs were composed of neurofilaments and expanded mitochondria. By literature review, ALS with p. L127S disclosed a male-dominant incidence rate, a variety of ages at onset, and low penetrance. The initial symptom was exclusively lower limb weakness. One-third of the patients only showed lower motor neuron signs and half did not present with bulbar symptoms. The neuropathological findings commonly observed in ALS with p. L127S variants were mainly the degeneration of lower motor neurons and the sensory system, including the posterior column, Clarke's nucleus, and the associated cerebellar system. The formation of intracytoplasmic hyaline inclusions was also a prominent feature. ALS with p. L127S variant should be included in the possible diagnosis of slowly progressive muscle weakness in the lower extremities, with or without family history or upper motor neuron signs. The loss of lower motor neurons and the accumulation of neurofilaments in the remaining neurons are key to the pathological diagnosis for ALS with p. L127S variant.