[A case of a 17-year-old male with neurofascin-155 antibody-positive chronic inflammatory demyelinating polyradiculoneuropathy presenting with tremor and ataxia].

A 17-year-old male with no medical history noticed weakness of his limbs with imbalance and subsequent finger tremors. Physical examination revealed features of polyneuropathy, including diffuse weakness, distal symmetrical numbness with impaired deep sensation and areflexia in all limbs. Postural tremor was present in fingers. Ataxia was apparent in both lower limbs, causing a wide-based gait with a positive Romberg sign. Cerebrospinal fluid contained elevated total protein without pleocytosis. A nerve conduction study disclosed demyelinating features with prolonged terminal latencies, slow velocities with delayed F-wave latencies, and prominent temporal dispersion. These findings led to diagnosis of typical chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with notable feature of postural finger tremor and ataxia of unknown cause. These atypical features prompted us to examine neurofascin-155 (NF155) antibodies, which were positive. No significant improvement occurred after initial administration of intravenous immunoglobulin and subsequent plasma exchange. However, corticosteroids with intravenous pulse therapy followed by oral prednisolone significantly improved the symptoms. Patients with CIDP with anti-NF155 antibodies may have similar clinical features and constitute a CIDP subgroup. In such patients, corticosteroids may be more effective than intravenous immunoglobulin. Further studies are needed to define the features of this subgroup and determine effective therapy for CIDP.