Individualized repetitive intravenous immunoglobulin therapy for a 79-year-old patient with GlyR antibody-positive PERM: a case report and literature review.

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare, life-threatening variant of stiff-person spectrum disorder that is primarily associated with anti-glycine receptor (GlyR) antibodies. Although advanced age and intensive care unit admission have been associated with poor outcomes for patients with GlyR antibody-positive PERM, detailed management strategies for elderly patients with multiple comorbidities remain limited. We report the successful individualized management of a 79-year-old male with glycine receptor 1 (GlyR1) antibody-positive PERM, who is among the oldest reported survivors of severe PERM. The patient initially presented with paroxysmal limb spasms, which were misattributed to spinal degeneration and a minor thalamic infarction. The subsequent development of a prominent startle response, respiratory failure, and autonomic instability prompted an autoimmune evaluation, confirming the presence of anti-GlyR1 antibodies in both serum and cerebrospinal fluid. High-dose corticosteroid pulse therapy was avoided because of an active pulmonary infection and comorbidity-related safety concerns. Intravenous immunoglobulin (IVIg) was selected as the initial immunomodulatory therapy, while plasma exchange was deferred and later discontinued after a single session because of procedure-related complications and hemodynamic instability. The patient received three sequential courses of IVIg; in addition, a single 20-mg subcutaneous dose of ofatumumab was administered as individualized off-label sequential/salvage immunotherapy. A major clinical improvement, including a reduction in spasms, successful extubation, antibody seroconversion, and excellent functional recovery with a modified Rankin scale (mRS) score of 1, occurred after repeated IVIg courses. At the 12-month follow-up, the patient remained clinically stable and had sustained negative GlyR1 antibody results. This case report highlights the importance of the early recognition of stimulus-sensitive spasms and the startle response in elderly patients with misleading age-related imaging findings. These findings also suggest that repeated IVIg courses may represent a feasible salvage strategy when conventional immunotherapies are limited, but the independent therapeutic contribution of ofatumumab remains uncertain. Serial GlyR1 antibody titers may be useful for monitoring the treatment response, although this result requires confirmation in larger studies.