Primary Progressive Multiple Sclerosis With Acute Neurologic Deterioration Secondary to Metabolic Derangements and Medication Effects.

A 73-year-old man with a 33-year history of primary progressive multiple sclerosis (PPMS) presented with subacute gait instability, confusion, dysarthria, and severe muscle spasms. Laboratory evaluation revealed severe acute kidney injury and hypercalcemia, while noncontrast brain MRI demonstrated chronic periventricular demyelinating changes without new inflammatory lesions; contrast-enhanced MRI was not obtained. The clinical picture was most consistent with a metabolically driven pseudoexacerbation precipitated by hypercalcemia from prolonged immobilization, nephrotoxic polypharmacy, and subtherapeutic gabapentin dosing, though concurrent inflammatory PPMS activity could not be excluded. Treatment with high-dose intravenous methylprednisolone, intravenous fluid resuscitation, and calcitonin resulted in normalization of renal function and serum calcium and meaningful improvement in neurologic symptoms. This case underscores the importance of thorough systemic evaluation before attributing acute neurologic deterioration in PPMS to inflammatory relapse.