Isolated Hypercapneic Respiratory Failure as a presentation of GBS variant: a paraneoplastic association?

Guillain-Barré Syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy, with the Pharyngeal-Cervical-Brachial (PCB) variant being a rare subtype. We report a 60-year-old male presenting with isolated hypercapnic respiratory failure and pulmonary embolism, subsequently diagnosed with PCB-GBS. The patient exhibited cranial and cervical weakness with preserved lower limb strength, cerebrospinal fluid albumino-cytological dissociation, and cervical root enhancement on MRI. Treatment with intravenous immunoglobulin led to rapid recovery. Evaluation for paraneoplastic etiology revealed an oncocytic follicular thyroid neoplasm, managed with thyroidectomy. This case underscores the importance of considering PCB-GBS in unexplained respiratory failure and highlights the rare paraneoplastic association with thyroid malignancy.