Atypical Acute Motor Axonal Neuropathy (AMAN) Presenting Concurrently With Community-Acquired Pneumonia and Respiratory Failure: A Case Report

A 36-year-old female presented with rapidly ascending, flaccid quadriparesis, bulbar, and respiratory failure requiring four days of mechanical ventilation. This presentation was highly atypical, as the neurological symptoms commenced virtually concurrently with an active community-acquired pneumonia (CAP), noted on the fourth day of her febrile prodrome, departing from the classic post-infectious timeline of Guillain-Barré syndrome (GBS). Initial investigations ruled out myopathy (normal creatine phosphokinase (CPK)/creatine kinase-MB (CK-MB)), while subsequent studies established the diagnosis. Nerve conduction velocity (NCV) confirmed non-length-dependent axonal motor polyneuropathy, and cerebrospinal fluid analysis showed albuminocytologic dissociation. The prompt suspicion and diagnosis of acute motor axonal neuropathy (AMAN) allowed for initiation of intravenous immunoglobulin (IVIG) and broad-spectrum antibiotics for the CAP, which resulted in a successful clinical course, including successful extubation, and impressive motor recovery upon discharge. This case report highlights the critical importance of recognizing parainfectious AMAN presentations to ensure timely immunomodulatory therapy in the setting of severe concurrent systemic illness.