This case was reported in a literature article and described the occurrence of demyelinating polyneuropathy in a 19-year-old male patient who received Influenza vaccine Quadrivalent unspecified season. Concurrent medical conditions included hereditary neuropathy with liability to pressure palsies. On an unknown date, the patient received Influenza vaccine Quadrivalent unspecified season at an unknown dose. On an unknown date, 14 days after receiving Influenza vaccine Quadrivalent unspecified season, the patient experienced demyelinating polyneuropathy (serious criteria GSK medically significant), hereditary neuropathy with liability to pressure palsies, condition aggravated, numbness of extremities, tingling of extremity, weakness in extremity, winged scapula, pes cavus and tendon reflex absent. The patient was treated with Immunoglobulin. On an unknown date, the outcome of the demyelinating polyneuropathy, hereditary neuropathy with liability to pressure palsies, condition aggravated, numbness of extremities, tingling of extremity, weakness in extremity, pes cavus and tendon reflex absent were unknown and the outcome of the winged scapula was recovered/resolved. The reporter considered the demyelinating polyneuropathy, hereditary neuropathy with liability to pressure palsies, condition aggravated, numbness of extremities, tingling of extremity, weakness in extremity, winged scapula, pes cavus and tendon reflex absent to be related to Influenza vaccine Quadrivalent unspecified season. Additional information was provided. This case was reported in a literature article and described the aggravated hereditary neuropathy with liability to pressure palsies (HNPP) in a 19-year-old male who was vaccinated with unspecified influenza vaccine (manufacturer unknown). The patient was previously healthy. The patient had no significant medical history. The patient's father had arterial hypertension and high feet arches but no weakness. The patient denied any previous episodes of wrist drop, foot drop or numbness, and tingling. The patient had not taken any prescription medicines and denied tobacco, alcohol, and illicit drug use. The patient exercised regularly, as part of his training. No information on patient's concomitant medication or concurrent condition was provided. On an unspecified date, the patient received unspecified influenza vaccine (administration site and route; dosages unknown; batch number not provided). The age of vaccination was not provided. On an unspecified date, 2 weeks after vaccination, the patient had onset of numbness, tingling, and weakness in both upper and lower extremities and did 20 push-ups (part of his physical fitness exam) the night before his symptoms started. Subsequently, the patient was presented to the hospital with 2 weeks history of symptoms. On physical examination, he had high feet arches and bilateral scapular winging. The overall reflexes were absent. Neurological examination showed Medical Research Council (MRC) strength of 3/5 in intrinsic hand muscles and finger extensors (other muscles including lower extremities were 5/5); decreased vibration and pinprick at toes and hands, absent deep tendon reflexes and a negative Babinski sign. Nerve conduction study (NCS) showed absent median sensory nerve action potential (SNAP), small ulnar and radial SNAPs with prolonged peak latencies, and sural SNAP amplitudes of 7 uV. Distal latency in ms for Median abductor pollicis brevis (APB) nerve in right side was 6.0 and left side was 4.6, distal latency in ms for ulnar abductor digiti minimi (ADM) nerve in right side was 5.1 and left side was 5.8, distal latency in ms for peroneal extensor digitorum brevis (EDB) nerve in right side was 5.5, distal latency in ms for tibial abductor halluces (AH) nerve in right side was 4.6, distal latency in ms for radial extensor indicis proprius (EIP) nerve in left side was 2.95, distal latency in ms for median digit 2 nerve in right side and left side was not recordable/absent, distal latency in ms for ulnar digit 5 nerve in right side was 4.12 and left side was 4.85, distal latency in ms for radial snuff nerve in right side was 2.95 and left side was 2.85, distal latency in ms for sural nerve in right side was 4.6. Compound motor action potential (CMAP) amplitudes in uV; sensory nerve action potential (SNAP) in uV for median APB nerve in right side was 1.1; 10.1 and left side was 0.2; 0.2, CMAP and SNAP for ulnar ADM nerve in right side was 4.1; 13.2; 4.1 and left side was 0.7; 0.7; 0.7, CMAP and SNAP for peroneal EDB nerve in right side was 6.1, 6.3, 5.6, CMAP and SNAP for tibial AH nerve in right side was 6.6, 5.1, CMAP and SNAP for radial EIP nerve in left side was 2.9, 2.3, 2.2, CMAP and SNAP for median digit 2 nerve in right side and left side was not recordable/absent, CMAP and SNAP for ulnar digit 5 nerve in right side was 5.2 and left side was 2.5, CMAP and SNAP for radial snuff nerve in right side was 14.9 and left side was 14.2, CMAP and SNAP for sural nerve in right side was 7. Conduction velocity in m/s for median APB nerve in right side was 42.4 and left side was 38.6, conduction velocity in m/s for ulnar ADM nerve in right side was 42.9, 53.5 and left side was 45.2, 42.6, conduction velocity in m/s for peroneal EDB nerve in right side was 39.8, 37.8, conduction velocity in m/s for tibial AH nerve in right side was 39.8, conduction velocity in m/s for radial EIP nerve in right side was 70.2, F wave latency (ms) for median APB nerve in right side was 34.2 and left side was not recordable/absent, F wave latency (ms) for ulnar ADM nerve in right side was 40.6 and left side was not recordable/absent, F wave latency (ms) for peroneal EDB nerve in right side was 61.5, F wave latency (ms) for tibial AH nerve in right side was 60.2. Nerve Conduction Study (NCS) results: Right and left sensory median NCS latency (ms) and AMP (mV) were non recordable/absent. Right sensory ulnar NCS latency (ms) and AMP (mV) were 4.12 and 5.2 respectively. Right sensory radial NCS latency (ms) and AMP (mV) were 2.95 and 14.9 respectively. Right sensory sural NCS latency (ms) and AMP (mV) were 4.6 and 7 respectively. Right sensory motor NCS latency (ms), distal response amplitude (AMP1) (mV) and CMAP amplitude below elbow (ulnar) or knee (peroneal) (AMP2); were 6, 1.1 and 1.0 respectively. Conduction velocity (CV) (m/s) right motor median was 42.4. F wave latency (ms) for right motor median was 34.2. Right motor ulnar NCS latency (ms), AMP1, AMP2, CMAP amplitude above elbow (ulnar) or knee (peroneal) (AMP3) (mV), 5.1, 4.1, 4.1 and 1.5 respectively. CV for right motor ulnar was 42.9 and 43.5. F-wave latency for right motor ulnar was 40.6. Right motor peroneal NCS latency (ms), AMP1, AMP2, (AMP3) (mV) were 5.5, 6.1, 5.6 and 5.7 respectively. CV for right motor peroneal was 39.8 and 39.2. F-wave latency for right motor peroneal was 61.5. Right motor tibial NCS latency (ms), AMP1 and AMP2, (mV) were 4.6, 6.6 and 5.8 respectively. CV for right motor tibial was 39.8. F-wave latency for right motor tibial was 60.2. Left sensory ulnar NCS latency (ms) and AMP (mV) were 4.85 and 2.5 respectively. Left sensory radial NCS latency (ms) and AMP (mV) were 2.85 and 14.2 respectively. Left NCS sensory motor median latency (ms), distal response amplitude (AMP1) (mV) and CMAP amplitude below elbow (ulnar) or knee (peroneal) (AMP2): were 4.6, 0.2 and 0.2 respectively. Conduction velocity (CV) (m/s) left motor median was 38.6. F-wave latency (ms) for left motor median was not reported/absent. Left NCS motor ulnar latency (ms) AMP1, AMMP2, AMP3 were 5.8, 0.7, 0.7 and 0.7 respectively. Conduction velocity (CV) (m/s) left motor ulnar was 45.2 and 42.6. F-wave latency (ms) for left motor ulnar was not reported/absent. Bilateral median and ulnar motor NCS showed prolonged onset latencies, small compound motor action potential (CMAP) amplitudes, slow conduction velocities, and prolonged F-waves. Peroneal and tibial motor NCS showed normal onset latencies, CMAP amplitudes, and slightly slow conduction velocities (39 m/s). Electromyography showed active denervation in abductor pollicis brevis and first dorsal interosseous. Cerebrospinal fluid showed slightly elevated protein (48 mg/dL) and 3 white blood cells. Diagnosis of Guillain-Barre syndrome was made based on acute onset, sural sparing on NCS and prolonged latencies and F-waves. Intravenous immunoglobulin 2 g/kg divided into 4 doses was administered with minimal clinical improvement. Although he had no neurological history, the symptom onset after vigorous exercise, the presence of high foot arches and scapular winging led us to suspect hereditary neuropathy with liability to pressure palsies (HNPP), and genetic testing was ordered. The patient was found to have PMP22 gene deletion, consistent with diagnosis of HNPP. At 2 months follow-up scapular winging had resolved, and median and ulnar CMAP amplitudes have returned to normal, but there was electrophysiological evidence of median neuropathy at the wrist and ulnar neuropathy at the elbow. Sural SNAP amplitude was 6 uV. The outcome of the event was not reported. At 2 month follow up median neuropathy at wrist and ulnar neuropathy at elbow. Distal latency in ms for Median APB nerve in right side was 4.65, distal latency in ms for ulnar ADM nerve in right side was 3.05, distal latency in ms for peroneal EDB nerve in right side was 5.5, distal latency in ms for tibial AH nerve in right side was 6.1, distal latency in ms for median digit 2 nerve in right side was 4.3, distal latency in ms for ulnar digit 5 nerve in right side was 3.45, distal latency in ms for sural nerve in right side was 4.5. Compound motor action potential (CMAP) amplitudes in mV; sensory nerve action potential (SNAP) in mV for median APB nerve in right side was 1.0; 9.6, CMAP and SNAP for ulnar ADM nerve in right side was 12.2, 1.5, 9.5, CMAP and SNAP for peroneal EDB nerve in right side was 5.1, 5.7, 5.3, CMAP and SNAP for tibial AH nerve in right side was 5.8, 4.3, CMAP and SNAP for median digit 2 nerve in right side was 6.2, CMAP and SNAP for ulnar digit 5 nerve in right side was 3.4, CMAP and SNAP for sural nerve in right side was 6. Conduction velocity in m/s for median APB nerve in right side was 52.5, conduction velocity in m/s for ulnar ADM nerve in right side was 43.5, 42.6, conduction velocity in m/s for peroneal EDB nerve in right side was 39.2, 42.6, conduction velocity in m/s for tibial AH nerve in right side was 40, F wave latency (ms) for median APB nerve in right side was 33.3, F wave latency (ms) ulnar ADM nerve in right side was 36.5, F wave latency (ms) for peroneal EDB nerve in right side was 64.6, F wave latency (ms) for tibial AH nerve in right side was 66.4. The authors commented "we postulate that, in our previously asymptomatic patient, the influenza immunisation triggered a mild transient autoimmune reaction that coupled with excessive exercise led to his acute neuropathy". The authors concluded, "HNPP can present acutely with a generalised neuropathy even in people who train regularly. Careful history and physical examination for foot deformities, scapular winging, and associated entrapment neuropathies can aid in the diagnosis".