Unmasking the Uncommon: A Rare Case Report of Submucosal Lipomatosis of the Appendix Mimicking Acute Appendicitis

Acute Appendicitis (AA) is a common medical emergency that presents with pain in the right iliac fossa and can mimic many other non neoplastic entities that clinically present as acute abdomen, such as intestinal obstruction, adhesions and perforation. Intestinal Submucosal Lipomatosis (SML) is a rare condition with a prevalence rate of 0.2%; however, it is even rarer in the appendix. Although SML can follow a varied course, it most commonly leads to AA or more serious complications like intestinal intussusception or massive intra-abdominal bleeding. Since AA can be a sequela of SML, it can obscure the true cause of inflammation on radiologic imaging due to wall thickening. Therefore, appendectomy, along with Histopathological Examination (HPE), is mandatory for diagnosing Appendiceal Submucosal Lipomatosis (ASL) and preventing complications associated with it. SML can be diffuse or focal and is microscopically characterised by the presence of increased mature adipocytes in the submucosal layer of the gastrointestinal tract, without a capsule—unlike lipoma—making this an important distinguishing feature between the two. Present case is of a 22-year-old male who presented to the surgical outpatient department with complaints of recurrent abdominal pain. Clinically, and even on radiology, it mimicked AA due to wall thickening but was later confirmed as SML of the appendix based on the final HPE report. This case highlights that an accurate preoperative diagnosis of SML, based on radiological findings of fat infiltration in the wall, can avoid laparoscopic appendectomy unless there is some associated complication; in some scenarios, it can also prevent potential complications.