[Clinical analysis of a motor neuron disease-like phenotype associated with anti-IgLON5 disease]

We report a case of anti-IgLON5 disease with a motor neuron disease-like presentation admitted to the Department of Neurology, Xuanwu Hospital, Capital Medical University in July 2021. The patient was a 71-year-old female who presented with the chief complaint of limb weakness persisting for 4 months. She showed progressive limb weakness accompanied by muscle atrophy. Electromyography (EMG) revealed extensive neurogenic damage. Initial serum evaluation for neural-specific autoantibodies was positive for IgLON5-Ab (1∶100). Repeat testing confirmed IgLON5-Ab positivity with a titer of 1∶1 000. The patient was diagnosed with anti-IgLON5 disease and treated with methylprednisolone and immunoglobulin, leading to clinical improvement. We found four relevant articles reporting a total of 11 similar cases. Thus, in this study, we analyzed a total of 12 cases, including our patient. Based on their clinical manifestations, these cases can be categorized into two types: amyotrophic lateral sclerosis(ALS)type and isolated bulbar type. Six cases-three males and three females-presented with the ALS type. Of these, three cases had diffuse limb weakness accompanied by muscle atrophy(two cases had diffuse hyperreflexia and one had a normal tendon reflex); one case presented with neck extensor weakness and bilateral asymmetric upper extremity weakness and was hyperreflexic at the bilateral patellar tendons; one case displayed asymmetric weakness in both lower limbs with normal deep reflexes, and one case exhibited neck weakness with hyperreflexia. EMG revealed diffuse lower motor neuron disease involving two or three regions. All patients tested positive for serum anti-IgLON5 antibodies. Four were also positive for anti-IgLON5 antibodies in cerebrospinal fluid, two were negative, and six were not tested. Among the 11 patients who received immunotherapy, 4 showed partial improvement in clinical symptoms, 2 exhibited transient improvement, 2 remained stable, and 3 showed no improvement. Testing for IgLON5-Ab should be considered among patients presenting with bulbar symptoms or ALS-like features, especially those with acute or subacute onset, rapid progression, autonomic dysfunction, vocal cord paralysis requiring tracheotomy, cognitive impairment, or involuntary movements. Early diagnosis and treatment may improve clinical symptoms and reduce adverse outcomes.