Chemical Pancreatitis Associated With Primary Systemic Amyloidosis Infiltrating the Pancreas

Abstract

Primary systemic AL amyloidosis is characterized by widespread extracellular deposition of fibrilforming monoclonal immunoglobulin light chains commonly associated with plasma cell dyscrasias. GI involvement is largely hepatic and luminal but clinical manifestations are highly variable. Pancreatic involvement is particularly rare. We present a case of systemic AL amyloidosis infiltrating the pancreas in the setting of newly diagnosed multiple myeloma. A 56 year-old man presented with worsening abdominal pain, nausea and vomiting after recent admission for epigastric pain and a lipase of 3000. He tolerated oral intake but noted 30 pounds of unintentional weight loss over three months, early satiety, and orthostatic syncope. He denied use of alcohol or medications. He had epigastric tenderness, tender hepatomegaly, and diffuse muscle wasting. Lipase was 3271 (73-393 U/L), alkaline phosphatase 160 (45-117 U/L), and hemoglobin 8 g/dL. A protein gap and nephrotic-range proteinuria were also observed. The remaining hepatic indices, triglycerides, calcium and IgG4 level were unremarkable. CT abdomen and EGD/EUS revealed a normal appearing pancreas, common bile duct without stones, no focal masses or calcifications and diffuse liver enlargement. Fine needle biopsy of the liver yielded nonrepresentative pancreatic acinar tissue with peri-acinar eosinophilic material staining positive for Congo red largely within the small vessels consistent with amyloidosis. Amyloid was also seen in biopsies of the heel fat pad, stomach, and liver. A monoclonal IgA kappa spike and a 20% population of bone marrow kappa restricted plasma cells confirmed the diagnosis of AL amyloidosis secondary to multiple myeloma (MM). He began treatment for MM however had subsequent exacerbations of his presenting symptoms with a persistently elevated lipase (>2000) on repeat admissions. Reports of systemic amyloidosis involving the pancreas range across asymptomatic infiltration to invariably fatal pancreatitis as a result of inflammatory AA amyloidosis. In these cases amyloid deposition was predominately perivascular resulting in small vessel obstruction. This case is unique in that it histopathologically resembles previous cases of pancreatic amyloidosis but manifested as a clinically milder chemical, subacute pancreatitis with a persistently elevated lipase. Although rare, pancreatic amyloidosis emphasizes the diverse GI manifestations of systemic amyloidosis.