AA Amyloidosis with Gastrointestinal, Mesenteric, and Omental Involvement in a Patient with Crohn’s Disease and Familial Mediterranean Fever: A Rare Case Report

Introduction

Amyloidosis represents a heterogeneous group of disorders characterized by the extracellular deposition of misfolded protein fibrils, which can lead to progressive organ dysfunction over time and may affect multiple organ systems1. The clinical presentation varies widely depending on the extent of disease and the organs involved, often resulting in delayed diagnosis and recognition at advanced stages1,2. Although gastrointestinal involvement is relatively uncommon, it may be easily overlooked in clinical practice due to its non-specific manifestations. Furthermore, involvement of the mesentery and omentum is exceedingly rare and has been reported only in a limited number of cases in the literature3,4. Depending on the underlying pathophysiological mechanism, amyloidosis may present as a systemic disease or, less frequently, as a localized process confined to a specific organ or tissue2. In this study, we aimed to present a rare case of AA amyloidosis involving the gastrointestinal tract, mesentery, and omentum in a patient with a history of chronic inflammatory disease.

Case Presentation

A 29-year-old male with a long-standing history of Crohn’s disease and Familial Mediterranean Fever (FMF) presented to the emergency department with complaints of nausea, recurrent episodes of vomiting, and inability to pass gas or stool for the past 3–4 days. His medical history was notable for prior cholecystectomy and appendectomy. Approximately six months earlier, a gastric biopsy obtained during endoscopy had been reported as histopathologically consistent with amyloidosis.

On physical examination, marked abdominal distension and diffuse tenderness were observed, along with decreased bowel sounds. An upright abdominal radiograph demonstrated multiple air–fluid levels, raising suspicion for intestinal obstruction, and the patient was subsequently admitted to the general surgery department for further evaluation and management. Nasogastric decompression was initiated, oral intake was discontinued, and conservative treatment was commenced. Contrast-enhanced computed tomography revealed adhesions likely related to previous surgical interventions, as well as multiple nodular lesions in the mesentery and omentum, raising concern for an infiltrative process or lymphadenopathy4,5. Due to the persistence of clinical findings and radiological suspicion, surgical intervention was undertaken. During the operation, adhesiolysis was performed to relieve bowel obstruction, and an omental biopsy was obtained for diagnostic purposes (Figure 1). The patient’s postoperative course was uneventful, with gradual clinical improvement, resumption of bowel function, and tolerance of oral intake. He was discharged in good condition on postoperative day 5. Histopathological examination of the omental tissue confirmed amyloid deposition, establishing the diagnosis (Figure 2, Figure 3).

Figure 1. Intraoperative image showing nodular involvement of the omentum and mesentery.

Figure 2. Histopathological examination showing amorphous eosinophilic deposits in omental tissue (Hematoxylin-Eosin staining).

Figure 3. Congo red staining demonstrating amyloid deposition with characteristic apple-green birefringence under polarized light.

Discussion

Amyloidosis represents a complex and heterogeneous group of disorders characterized by the abnormal misfolding of various precursor proteins into insoluble fibrillar structures, which subsequently accumulate within the extracellular matrix of tissues, ultimately leading to progressive organ dysfunction and involvement of multiple organ systems1,2. The gold standard for diagnosis remains Congo red staining, through which amyloid deposits exhibit the characteristic apple-green birefringence under polarized light, providing a definitive histopathological confirmation6. Among the various subtypes, AL and AA amyloidosis are the most frequently encountered in clinical practice, with AA amyloidosis being particularly associated with chronic inflammatory conditions such as Crohn’s disease and Familial Mediterranean Fever (FMF); this association is largely attributed to persistently elevated levels of serum amyloid A protein secondary to ongoing inflammation7,8. Although gastrointestinal involvement is relatively uncommon, it poses significant diagnostic challenges due to its tendency to present with non-specific symptoms, including abdominal pain, diarrhea, malabsorption, and weight loss, all of which may overlap with a wide range of other gastrointestinal disorders9,10. Consequently, this nonspecific clinical presentation often leads to delayed diagnosis or incidental detection during evaluation for other conditions. Indeed, gastrointestinal amyloidosis remains a rare entity in clinical practice, and its subtle and variable symptomatology frequently contributes to under-recognition or misdiagnosis11. Furthermore, systemic amyloidosis is characterized by a highly variable clinical course owing to its ability to affect multiple organs to differing extents, thereby necessitating a multidisciplinary approach for accurate diagnosis, comprehensive evaluation, and optimal management12. Involvement of the mesentery and omentum is exceedingly rare and has been reported only in a limited number of cases in the literature. Importantly, such involvement may radiologically mimic malignant or lymphoproliferative processes, thereby complicating the differential diagnosis and often prompting further invasive diagnostic procedures4,5. For this reason, definitive diagnosis in such cases typically relies on histopathological examination. In the present case, it is considered that the coexistence of Crohn’s disease and FMF contributed to the development of AA amyloidosis through chronic inflammatory mechanisms, with disease progression leading to simultaneous involvement of the gastrointestinal tract, mesentery, and omentum. Moreover, the intraoperatively observed omental nodularity supports the macroscopic infiltrative nature of amyloid deposition, further corroborating the pathological findings.

Conclusion

This case illustrates a rare presentation of AA amyloidosis involving the gastrointestinal tract, mesentery, and omentum, and highlights the variable and often insidious clinical course of the disease. Amyloidosis should be considered in the differential diagnosis of patients presenting with unexplained gastrointestinal symptoms, particularly in those with a history of chronic inflammatory conditions. Early recognition, together with appropriate histopathological evaluation, is essential for improving patient outcomes and ensuring optimal management of the disease process.