Introduction: Light chain amyloidosis (AL) is a rare condition characterized by multisy stem involvement. Due to the non-specific nature of its symptoms, there is often a significant delay between the onset of symptoms and a definitive diagnosis. Here, we present the case of a patient with predominant gastrointestinal and cardiac involvement. Case report: A previously healthy 64-year-old female presented with a six-month history of asthenia, 15 kg weight loss with preserved appetite and chronic diarrhea. Upper endoscopy revealed erosive gastropathy and villous atrophy, later confirmed as systemic amyloidosis by duodenal biopsy with positive Congo Red staining. The patient developed pleuritic pain and pleural effusion, leading to a diagnosis of pneumonia. Cardiac studies revealed amyloid car diomyopathy. Stage III amyloidosis AL with lambda light chains was diagnosed. During her hospitalization, the patient required a pacemaker due to cardiac rhythm disturbances and began chemotherapy with the CyBorD regimen, with good clinical response. She is currently receiving outpatient treatment, with good tolerance to the second cycle of chemotherapy. Discussion: In our patient, the diagnosis of amyloidosis AL was primarily based on histological findings in the gastrointestinal tract. Of note was the rapid cardiac involvement, making it challenging to optimize pharmacological treatment. We highlight this case due to the rarity of the disease and the significant therapeutic challenges it presents.