A 70 year old lady presents with generalised weakness and fatigability for 8 months. She had no other complaints, while her medical and surgical histories are unremarkable. Her FBC is significant for a Hb of 5.4 g/dL, along with a low MCV, MCHC and MCH. Her electrolytes, liver functions, renal functions, and coagulation profiles are normal. Repeated questioning reveals a history of intermittent tarry colored stools. Initial and repeat upper GI endoscopies are normal, as is a colonoscopy.
You realize that a barium series may obscure any overt bleeding, and potentially interfere with subsequent investigations.
There is active bleeding from the proximal jejunum; the mucosa in that region appears nodular, polypoid, and eroded. The remainder of the jejunum shows thickening of the valvulae conniventes.
Congo red staining of jejunal biopsies reveals extensive, dense, homogenous deposits in the lamina propria and submucosa, with apple-green birefringence with polarized light; the hematoxylin stain reveals amorphous, salmon-pink, sparsely cellular hyaline material.
Serum protein electrophoresis and immunofixation reveal a monoclonal band of IgG lambda paraprotein.