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.