[Congo red-negative light chain disease with intractable diarrhea].

A 56-year-old man was admitted due to chronic diarrhea with progressive weight loss (30 kg within 1 year). All results of medical investigations were normal. The suspected diagnosis of a neuroendocrinological neoplasm could not be established; there was also no evidence for a lymphoma or amyloidosis. Chronic diarrhea and weight loss persisted over the ensuing weeks. Additionally, impairment of renal function and heart insufficiency with consecutive pericardial effusion as well as peripheral facial paralysis and peripheral neuropathy could be observed. Six months after hospital admission, the patient died due to progressive multiple organ failure. Postmortem examination revealed normal bone marrow. Only with additional immunohistochemical investigations of all organs could the diagnosis of a systemic Congo red-negative light chain disease be established.