Differentiating poor prognosis from treatment-related fluctuations in Guillain-Barré syndrome for repeating immunoglobulin treatment: an illustrative case report.

Background: Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy that may follow infectious triggers and can progress to severe weakness, cranial nerve involvement, autonomic dysfunction, and respiratory failure. Cytomegalovirus (CMV)-associated GBS is often linked to a more severe clinical course. Although intravenous immunoglobulin (IVIG) and plasma exchange are established first-line treatments, management becomes challenging when patients deteriorate after initial therapy, particularly when distinguishing poor prognosis from treatment-related fluctuation (TRF). Case presentation: We report the case of a 42-year-old woman who developed progressive paresthesias, diffuse pain, gait disturbance, areflexia, facial involvement, dysphagia, dysarthria, autonomic dysfunction, and later respiratory failure. Cerebrospinal fluid analysis showed albuminocytologic dissociation, electrodiagnostic studies supported acute polyradiculoneuropathy, and MRI demonstrated contrast enhancement of the facial nerve roots and cauda equina. Serum testing revealed CMV IgM positivity with detectable CMV DNA, consistent with CMV-associated GBS. The patient received IVIG and ganciclovir. After initial stabilization following the first IVIG course, she experienced sudden respiratory deterioration requiring intubation. Given the temporal pattern of stabilization followed by worsening, the episode was interpreted as TRF occurring in a patient with otherwise poor prognostic features. A second IVIG cycle was administered, followed by gradual respiratory and neurological improvement. Discussion: This case illustrates the clinical difficulty of deciding whether repeated immunotherapy is justified in severe GBS. Current evidence discourages routine second IVIG courses in patients with poor prognosis who fail to respond; however, this recommendation does not necessarily apply to TRF, where renewed immunotherapy may be considered. In this patient, post-IVIG stabilization followed by acute deterioration supported the interpretation of TRF; persistent CMV viremia was considered a possible marker of ongoing immune stimulation. Conclusion: CMV-associated GBS may follow a severe and fluctuating course. Careful distinction between poor prognosis, nonresponse, and treatment-related fluctuation is essential because it directly influences therapeutic decision-making. Close monitoring, individualized immunotherapy, intensive supportive care, and early rehabilitation remain central to optimizing outcomes in severe GBS.