A 39-year-old man had protracted vomiting after gastric plication for morbid obesity. Within three months he lost 53 kg in weight and developed neuromuscular weakness, especially in the lower extremities. Clinical and laboratory studies suggested both radicular and peripheral neuropathy. One year later the condition was only marginally improved: he took only few steps unsupported. The apparent etiology is malnutrition but the primary cause remained unknown.