An autopsy case of macroglobulinemia complicated with syndrome of inappropriate secretion of ADH (SIADH) like hyponatremia, hypopituitarism and AL amyloidosis.

An 88-year-old male patient with macroglobulinemia was admitted to our hospital because of severe hyponatremia and unconsciousness. Laboratory findings showed decreased inhibition of antidiuretic hormone (ADH) and he was diagnosed with syndrome of inappropriate secretion of ADH (SIADH). Hyponatremia improved with only limitation of water intake and the patient was followed up on a continuing outpatient basis. However, soon after discharge from hospital, his legs started swelling with edema and hyponatremia worsened. He was re-admitted due to a fall at home. Hyponatremia was observed at re-admission. A CRH challenge test showed partial dysfunction of ACTH secretion. Corticosteroid therapy was performed, but the patient subsequently died from pneumonia. Pathological findings at autopsy revealed invasion of plasma cells and amyloid depositions in multiple organs, including the pituitary, adrenal cortex, heart, liver, kidney, lymph nodes and bone marrow. Consistent with these results, fibrosis was observed in the anterior lobe of the pituitary, suggesting that the autopsy findings were related to the clinical observations and diagnosis. This is the first reported case of macroglobulinemia complicated with multiple hormone dysfunction.