Peripheral Myelin Protein 22 (PMP22) is mostly expressed in Schwann cells where it is essential in the compaction of myelin. The duplication of the PMP22 gene results in a hereditary demyelinating neuropathy of the Charcot-Marie-Tooth type 1A (CMT1A). So far there are only a few case reports suggesting that dysimmune mechanisms may take part in the pathophysiology of this disease. We describe three siblings carrying the duplication of the PMP22 gene, with a significant reduction of serum immunoglobulin G levels in all three cases and sural nerve vasculitis in the two women, which supports the proposition, that immune dysfunction may accompany this disease in some cases.