This medically confirmed literature case (initial receipt 20-Oct-2015) concerns a 71-year-old male patient. On an unspecified date, the patient received influenza vaccine (influenza virus vaccine, manufacturer and batch number not reported). On an unspecified date, 10 days after vaccination, the patient developed numbness in his hands and feet followed by severe generalized weakness, urinary retention and incontinence requiring Foley catheter. His CSF (cerebrospinal fluid) protein was elevated at 82 mg/dl with no pleocytosis. On admission, the patient also developed hyponatremia with sodium at 127 mEq/L.  The right median nerve motor conduction studies diagnosed GBS (Guillain-Barre Syndrome) (day 5). However, in month 9, the diagnosis was revised to chronic inflammatory demyelinating polyneuropathy (CIDP). The patient received treatment with IVIG for five days and his arms showed significant improvement. Six weeks later, weakness increased and the patient had new-onset of bilateral facial palsy with dyspnea and orthopnea. The nerve conduction studies showed conduction blocks in the forearms with slowing and absent F-waves. The patient was treated with another course of IVIG. The events of dyspnea and arm and facial strength improved but the patient remained non-ambulatory. The patient was in rehabilitation and his improvement plateaued for about 10 months, during which he could stand with 2-person assistance. The patient then developed rapid onset of increasing weakness and numbness in both hands with no significant change in the leg strength (which remained extremely weak). An EDx (electrodiagnostic) study was repeated and showed markedly decreased motor conduction velocities in the upper extremities bilaterally (10-14 m/s), prolonged distal latencies and prolonged F-wave latencies. In view of EDx findings, new onset of sensory loss, hand weakness and lack of improvement in leg strength, the patient was started on treatment with IVIg infusions at 2g/kg every 4 weeks. He responded dramatically to the treatment. The patient was seen after 5 IVIg pulse therapies and was able to stand on his own, walked independently with a walker and had normal strength in the upper extremities. A repeat EDx study showed remarkable improvement of CMAP amplitudes in the upper extremities. IVIg infusion intervals were extended gradually during the next 26 months to every 8 weeks. At the two year follow-up, the patient walked independently and had no weakness but there was reduced sensation in the legs and mild sensory ataxia. The outcome was reported as not recovered. Reporter's Comments: Reporter's comments: it was reported that the patient with acute-onset chronic inflammatory demyelinating polyneuropathy (A-CIDP) was initially diagnosed with severe GBS but was later confirmed to have CIDP based on the clinical course and electrodiagnostic (EDx) studies. Sender's Comments: Company comments: Seriousness: Serious. Hospitalisation. Listedness: Unlisted. Brand of vaccine not specified. Assessment according to the CCDS for CSL Inactivated Influenza Virus Vaccine and the Afluria PI, CIDP and all associated events are unlisted. Causality: Possible. Time to onset is 10 days following vaccination. Demyelinating disease such as GBS and CIDP can be explained as autoimmune neuropathies which can follow Influenza vaccination. No other risk factors such as preceding respiratory or gastrointestinal disease were specified. Influenza vaccination offers a plausible pathomechanism and temporal association hence causally attributable.