Efficacy of apheresis in antibody-negative progressive encephalomyelitis with rigidity and myoclonus.

Introduction: Progressive encephalomyelitis with rigidity and myoclonus (PERM) is characterized by brainstem symptoms, muscle rigidity, and myoclonus. While autoantibodies to inhibitory neurons have been associated with the pathology, about 30% of cases are negative for autoantibodies. There are few reported cases of antibody-negative PERM and its clinical course and prognosis are unknown.

Methods: We report three cases of antibody-negative PERM in which plasma exchange was effective.

Results: Case 1 was a 68-year-old man, case 2 was a 27-year-old woman, and case 3 was a 47-year-old woman. In all three cases, steroid pulse therapy and intravenous immunoglobulin had limited effect and plasma exchange was markedly effective. All patients experienced disease relapse, which was effectively treated with plasma exchange.

Conclusion: In the present cases of antibody-negative PERM, plasma exchange was most effective and was maintained long-term despite repeated relapses. Plasma exchange should be actively chosen in antibody-negative PERM.