Reader Response: Intravenous Immunoglobulin Therapy in Patients With Painful Idiopathic Small Fiber Neuropathy.

We read with great interest the recent article by Margot Geerts et al.1 The authors evaluated the efficacy of IV immunoglobulin (IVIG) in patients with idiopathic small fiber neuropathy (I-SFN). Immunologic mechanisms may be involved in the pathophysiology of some I-SFN.2 Previous studies showed that IVIG treatment is effective against immune-mediated SFN3-5; however, they found that IVIG treatment was not effective in 30 patients with I-SFN. Previous studies on SFN used IVIG for at least 5 consecutive days, and the pain was evaluated immediately after treatment.3-5 Alternatively, IVIG was administrated in this study for 2 consecutive days with a 3-week interval for 4 rounds based on a regimen for chronic inflammatory demyelinating polyneuropathy but not for SFN. The pain was evaluated at weeks 1 and 12 and month 6 after the first dose.1 Therefore, if the authors followed the protocols for SFN as in previous studies,3-5 they may have different conclusions on IVIG efficacy. The authors should compare the efficacy of 2 regimens about IVIG usage.