For patients with suspected CIDP, especially young individuals with sensorimotor neuropathy and proprioceptive impairment, testing and subclass determination of anti-CNTN1 and anti-PLA2R antibodies and the monitoring of antibody class switching may be necessary even when satisfactory short-term treatment effects have been obtained with immunotherapy. The gene discussed is CNTN1; the disease is chronic inflammatory demyelinating polyradiculoneuropathy.