Atypical Abdominal Pain: Uncovering Malignant Peritoneal Mesothelioma in Suspected Crohn's Disease: A Case Report

Background:
Malignant peritoneal mesothelioma (MPM) is a rare malignancy confined to the abdominal cavity. Most cases occur in Whites. Industrial pollutants including asbestos exposure is a well-known cause in pleural mesothelioma but less associated with peritoneal mesothelioma. Symptoms are variable and non-specific but predominantly include abdominal pain, abdominal distention, bloating, weight loss and early satiety. Due to non-specific clinical symptoms, diagnosis of MPM can often be delayed.
Methods:
We present a case report of reported ileal Crohn’s disease with an unexpected diagnosis of peritoneal mesothelioma. This case highlights the need for histologic confirmation of Crohn’s disease and thorough evaluation for other potential etiologies in complex cases. Clinical Case A 62-year-old White male with a history of diverticulitis was referred to an academic IBD center for reported ileal Crohn’s disease on Humira 40 mg every 2 weeks. The patient had constant stabbing abdominal pain for 3 years associated with constipation. He had fatigue and early satiety resulting in significant weight loss. He had no history of tobacco use. His mother had colon cancer, but otherwise, there was no family history of malignancy. He was diagnosed with ileal Crohn’s disease at an outside hospital based on video capsule endoscopy significant for scattered erosions in the ileum. Prior EGD and colonoscopies were unrevealing. He had multiple CT imaging studies with ileal thickening and moderate inflammatory fat stranding. He did not have iron deficiency or B12 deficiency. Fecal calprotectin was not performed. He did not have histologic confirmation of Crohn’s disease. His clinical symptoms did not improve while on Humira. He was given multiple intermittent courses of prednisone by his primary care provider or during ER visits.
Results:
His symptoms of abdominal pain resolved immediately with Prednisone. On evaluation at our center, Humira level was checked and was undetectable with moderate antibodies. Humira was discontinued. Magnetic resonance enterography (MRE) was performed and was largely unrevealing. Due to concern for possible other etiologies such as mesenteric adenitis or panniculitis to explain his symptoms, decision was made to perform a diagnostic laparoscopy. Diagnostic laparoscopy revealed peritoneal mesothelioma, confirmed by biopsy as diffuse, epithelioid type. The diagnosis was supported by positive staining for calretinin, pankeratin, CK7, and CK5/6. On further discussion with the patient, he worked on oil rigs and had exposure to asbestos as a radio technician.
Conclusions:
This case report highlights a rare, atypical presentation of peritoneal mesothelioma in a patient thought to have ileal Crohn’s disease, illustrating the complexities in diagnosing peritoneal mesothelioma. This case underscores the need for vigilant monitoring using objective markers like CRP, fecal calprotectin, and endoscopy with histologic confirmation to accurately diagnosis Crohn’s disease, assess disease activity and guide treatment. It is imperative to consider other etiologies particularly in the setting of non-specific symptoms to ensure appropriate diagnosis and treatment plan.