Isolated ectopic lung uptake of technetium 99m methylene diphosphonate on bone scintigraphy in primary amyloidosis

Pulmonary deposition of technetium 99m methylene diphosphonate was found on a bone scan of a patient with undiagnosed primary AL amyloidosis. Unusual clinical manifestations during the course of the disease led to a post-mortem diagnosis. The mechanisms for pulmonary and other ectopic soft tissue bone scan tracer depositions, as well as their significance in the diagnosis of amyloidosis, are discussed.