Clinical and serological insights into paraneoplastic brachial amyotrophic diplegia

Brachial amyotrophic diplegia (BAD) is typically linked to a neurodegenerative etiology such as amyotrophic lateral sclerosis (ALS). Clinical and serological characterizations of paraneoplastic neurologic syndromes resembling BAD are limited. A retrospective chart review of patients with BAD-like presentations was conducted. Clinical/paraclinical features of paraneoplastic BAD and neurodegenerative BAD cases were compared. Between 2017 and 2023, 13 cases of BAD were identified, of these 10 were neurodegenerative BAD (ALS variant), and 3 cases associated with paraneoplastic autoimmunity. An additional paraneoplastic BAD case diagnosed in 2005 was included. LUZP4-IgG was detected in all four paraneoplastic cases, with coexisting KLHL11-IgG in three cases and ANNA1 (anti-Hu)-IgG in one case. Out of the four paraneoplastic cases, two patients had seminoma, while the remaining two had limited cancer investigation. Three patients exhibited bi-brachial weakness as the initial symptom before the onset of brainstem symptoms or seizures. Compared to BAD patients with a neurodegenerative etiology, a higher proportion of paraneoplastic cases had ataxia (75