Severe enteropathy caused by α-heavy chain disease lacking detectable M-proteins.

A 57-year-old Japanese man was admitted to our hospital with diarrhea, weight loss and malabsorption. Due to a high serum IgA level, we suspected α-heavy chain disease (α-HCD). However, no monoclonal IgA was detected on protein electrophoresis or immunofixation. Immunohistochemical staining of intestinal biopsy specimens showed proliferation of CD138(+)IgA(+) cells, compatible with a diagnosis of α-HCD. Most α-HCD patients exhibit M-proteins in the serum on electrophoresis or immunoelectrophoresis; however, some patients lack detectable M-proteins, similar to our patient. Therefore, when α-HCD is suspected based on the clinical features, immunohistochemistry is required to make a diagnosis.