The term "cocoon syndrome" defines a sclerosing encapsulating peritonitis (SEP) that involves a chronic fibrotic inflammatory reaction of the parietal peritoneum and of the viscera leading to a complete sclerosis. The cocoon that is formed causes an incarceration of the intestinal loops with severe complications leading to high mortality. We are presenting the case of a 15-year-old young man that underwent surgery for appendectomy and that was evaluated for having a regular abdominal state. During the post-surgery period, however, several episodes of intestinal occlusion required further surgical interventions leading to a right hemicolectomy. The presence of a fibrotic-adhesive ligneous peritonitis with blended intestinal loops, severely thickened walls, and intestinal scaring stenosis was observed during his second surgical operation. A stenosis of the colostomy led to a worsening of the vital signs of the young man with the onset of a cardiac failure and subsequent decease. Macroscopic autopsy examination and histological analysis confirmed the severe obstructive adhesive encapsulating abdominal context allowing to trace back the cause of death to a cocoon syndrome. Since no predisposing factor could be found, we hypothesized that this case could be characterized by an excessive peritoneal reactivity due to surgical appendectomy. Cocoon syndrome is a rare pathology, and its microscopic features are seldomly observed and could be underestimated. We present a directly observed case with a very substantial macroscopic and microscopic context.