Relapsing-Remitting Immunotherapy Responsive Small-Fiber Neuropathy: Longitudinal Tracking Through 10 Years Including Pregnancies

OBJECTIVES To expand understanding of the pathogenesis, presentations, and treatment of initially idiopathic small fiber polyneuropathy (SFN). METHODS We longitudinally readministered validated metrics to track disease course and treatment responses in a previously healthy woman with acute, postinfectious, skin biopsy-confirmed, idiopathic SFN. RESULTS During 5 years, viral respiratory infections triggered 3 separated episodes of acute, disabling burning hand, foot, and face pain (erythromelalgia). The initial 2 resolved with high-dose prednisone, and the third responded to repeated immunoglobulin treatments. Pregnancy with miscarriage triggered a fourth exacerbation refractory to corticosteroids and cyclosporin. Immunoglobulins restored total remission for 2 months; then, 2 rituximab doses slightly improved later flaring. Subsequently, daratumumab initiated 100-day remission later maintained by belimumab, initiated to permit another pregnancy. Remission continued after gestational week 13 all-treatment withdrawal. A week 30 fifth flare responded to plasmapheresis, with healthy birth at week 40. At 11-week postpartum, as symptoms returned, restarting belimumab restored remission maintained during ≥19 months of breastfeeding. DISCUSSION This decade of tracking characterizes a relapsing-remitting course of SFN with initially separated monophasic episodes becoming more confluent, as with multiple sclerosis. This tempo and responsiveness to 5 immunotherapies suggest dysimmune causality. Validated metrics helped define the course and track treatment efficacy, particularly during pregnancy and breastfeeding. CLASSIFICATION OF EVIDENCE This is a single observational study without controls. This provides Class IV evidence.