Inappropriate secretion of antidiuretic hormone in a patient with chronic inflammatory demyelinating polyneuropathy.

A 54-year-old man suffered from a relapse of chronic inflammatory demyelinating polyneuropathy (CIDP), and developed quadriplegia and somnolence requiring mechanical ventilation for respiratory failure. Serum Na concentration remained at low levels during the clinical course, and a diagnosis of inappropriate secretion of antidiuretic hormone (SIADH) was made. The present case had not only acute aggravation of CIDP with autonomic dysfunction but also intracranial hypertension caused by increased CSF protein (maximum level, 1,315 mg/dl). It seemed likely that injury of the afferent fibers of the baroregulatory pathway or intracranial hypertension might have contributed to SIADH in this patient.